diff --git a/data/plans.json b/data/plans.json
index a812161..9844288 100644
--- a/data/plans.json
+++ b/data/plans.json
@@ -5,12 +5,12 @@
     "description": "Welcome! This is a sample practice plan — edit it, or create your own from the Plans tab.",
     "items": [
       {
-        "trackId": "demo-song",
+        "trackChoices": ["demo-song"],
         "tasks": [{ "type": "playWithTrack", "count": 2 }],
         "dice": false
       },
       {
-        "trackId": "a-major-scale",
+        "trackChoices": ["a-major-scale"],
         "tasks": [{ "type": "playWithoutTrack", "count": 1 }],
         "dice": true
       }
diff --git a/src/app/PracticeTasksList.tsx b/src/app/PracticeTasksList.tsx
index 90195c8..3ec291e 100644
--- a/src/app/PracticeTasksList.tsx
+++ b/src/app/PracticeTasksList.tsx
@@ -3,7 +3,7 @@
 import DiceRoller from "./DiceRoller";
 import TaskList, { TaskTypeDef } from "./TaskList";
 import TrackNote from "./TrackNote";
-import type { PracticeItem, Track } from "./plans";
+import { primaryTrackId, type PracticeItem, type Track } from "./plans";
 import type { Student } from "./students";
 
 interface Props {
@@ -19,11 +19,12 @@ export default function PracticeTasksList({ items, tracks, taskTypes, doneTasks,
   return (
     <ul className="space-y-4">
       {items.map((item) => {
-        const track = tracks.find((t) => t.id === item.trackId);
+        const trackId = primaryTrackId(item);
+        const track = tracks.find((t) => t.id === trackId);
         return (
-          <li key={item.trackId} className="rounded-lg border bg-white p-4">
+          <li key={trackId} className="rounded-lg border bg-white p-4">
             <div className="flex items-center gap-2 mb-1">
-              <span className="font-semibold">{track?.name ?? item.trackId}</span>
+              <span className="font-semibold">{track?.name ?? trackId}</span>
               {track?.type === "video" && (
                 <span className="text-xs bg-zinc-100 text-zinc-500 rounded px-1.5 py-0.5">
                   video
@@ -36,7 +37,7 @@ export default function PracticeTasksList({ items, tracks, taskTypes, doneTasks,
               </p>
             )}
             <TaskList
-              trackId={item.trackId}
+              trackId={trackId}
               tasks={item.tasks}
               taskTypes={taskTypes}
               initialDone={doneTasks}
@@ -50,8 +51,8 @@ export default function PracticeTasksList({ items, tracks, taskTypes, doneTasks,
             )}
             {activeStudent.kind === "primary" && (
               <TrackNote
-                trackId={item.trackId}
-                initialNote={notesByTrack[item.trackId] ?? ""}
+                trackId={trackId}
+                initialNote={notesByTrack[trackId] ?? ""}
               />
             )}
           </li>
diff --git a/src/app/actions.test.ts b/src/app/actions.test.ts
index e54c243..00e1081 100644
--- a/src/app/actions.test.ts
+++ b/src/app/actions.test.ts
@@ -362,6 +362,42 @@ describe("addTrack + getTrackBlobUrl", () => {
   });
 });
 
+describe("getPlans — legacy trackId normalization", () => {
+  it("upgrades pre-#4 items that still carry a single trackId to trackChoices", async () => {
+    setupScheduleData({});
+    // Shape stored before #4: a bare trackId, no trackChoices.
+    setupPlansData([
+      {
+        id: "0",
+        createdDate: "2026-04-10",
+        items: [{ trackId: "twinkle", tasks: [{ type: "sing", count: 1 }], dice: false }],
+        checklist: [],
+      },
+    ]);
+    const { getPlans } = await loadActions();
+    const item = (await getPlans())[0].items[0];
+    expect(item.trackChoices).toEqual(["twinkle"]);
+    expect("trackId" in item).toBe(false);
+    // Other fields are preserved through the upgrade.
+    expect(item.tasks).toEqual([{ type: "sing", count: 1 }]);
+    expect(item.dice).toBe(false);
+  });
+
+  it("leaves already-migrated trackChoices items untouched", async () => {
+    setupScheduleData({});
+    setupPlansData([
+      {
+        id: "0",
+        createdDate: "2026-04-10",
+        items: [{ trackChoices: ["a", "b"], tasks: [], dice: true }],
+        checklist: [],
+      },
+    ]);
+    const { getPlans } = await loadActions();
+    expect((await getPlans())[0].items[0].trackChoices).toEqual(["a", "b"]);
+  });
+});
+
 describe("savePlan — inline reference tracks", () => {
   it("persists new reference tracks to the catalog alongside the plan", async () => {
     setupScheduleData({});
@@ -379,7 +415,7 @@ describe("savePlan — inline reference tracks", () => {
         id: "0",
         createdDate: "2026-04-10",
         description: "with custom practice",
-        items: [{ trackId: "a-major-scale", tasks: [], dice: false }],
+        items: [{ trackChoices: ["a-major-scale"], tasks: [], dice: false }],
         checklist: [],
       },
       [{ id: "a-major-scale", name: "A Major Scale", type: "reference", file: null }],
@@ -391,7 +427,7 @@ describe("savePlan — inline reference tracks", () => {
       type: "reference",
       file: null,
     });
-    expect((await getPlans())[0].items[0].trackId).toBe("a-major-scale");
+    expect((await getPlans())[0].items[0].trackChoices).toEqual(["a-major-scale"]);
     // Media-less => no blob entry written.
     expect(JSON.parse(readFileSync(blobsFile, "utf-8"))).toEqual({
       scale: "https://blob.example/scale.mp3",
diff --git a/src/app/actions.ts b/src/app/actions.ts
index a297d77..b9e4d8a 100644
--- a/src/app/actions.ts
+++ b/src/app/actions.ts
@@ -117,8 +117,25 @@ function nextPlanId(plans: Plan[]): string {
 
 // --- Public API ---
 
+// Upgrade legacy practice items that still carry a single `trackId` (the shape
+// stored in Redis before #4) to the `trackChoices` pool shape. Keeps prod data
+// working without a manual Redis migration.
+function normalizePlans(plans: Plan[]): Plan[] {
+  return plans.map((plan) => ({
+    ...plan,
+    items: plan.items.map((item) => {
+      if (Array.isArray(item.trackChoices)) return item;
+      const legacy = item as unknown as { trackId?: string };
+      const { trackId, ...rest } = legacy;
+      return { ...(rest as object), trackChoices: trackId ? [trackId] : [] } as typeof item;
+    }),
+  }));
+}
+
 export async function getPlans(): Promise<Plan[]> {
-  return readJson<Plan[]>(PLANS_KEY, PLANS_PATH, plansSeed as unknown as Plan[]);
+  return normalizePlans(
+    await readJson<Plan[]>(PLANS_KEY, PLANS_PATH, plansSeed as unknown as Plan[]),
+  );
 }
 
 function ensureTodayInSchedule(
diff --git a/src/app/plans.test.ts b/src/app/plans.test.ts
index 8869473..dc6f7a3 100644
--- a/src/app/plans.test.ts
+++ b/src/app/plans.test.ts
@@ -1,5 +1,6 @@
 import { describe, it, expect, beforeEach, vi } from "vitest";
 import { TEST_PRIMARY as PRIMARY, TEST_LINKED as LINKED } from "./test-support/people";
+import { primaryTrackId } from "./plans";
 
 async function loadPlans() {
   const mod = await import("./plans");
@@ -10,12 +11,24 @@ beforeEach(() => {
   vi.resetModules();
 });
 
+describe("primaryTrackId", () => {
+  it("returns the only track for a single-element pool", () => {
+    expect(primaryTrackId({ trackChoices: ["twinkle"], tasks: [], dice: false })).toBe("twinkle");
+  });
+
+  it("returns the first track of a multi-track pool (pre-dice active track)", () => {
+    expect(
+      primaryTrackId({ trackChoices: ["twinkle", "minuet"], tasks: [], dice: false }),
+    ).toBe("twinkle");
+  });
+});
+
 describe("getPlanForDate — happy path", () => {
   it("returns the plan for a scheduled date", async () => {
     vi.doMock("./actions", () => ({
       getSchedule: async () => ({ "2026-04-07": "0" }),
       getPlans: async () => [
-        { id: "0", createdDate: "2026-04-07", items: [{ trackId: "x", tasks: [], dice: false }], checklist: [] },
+        { id: "0", createdDate: "2026-04-07", items: [{ trackChoices: ["x"], tasks: [], dice: false }], checklist: [] },
       ],
     }));
     const { getPlanForDate } = await loadPlans();
diff --git a/src/app/plans.ts b/src/app/plans.ts
index fb50bc7..927bd45 100644
--- a/src/app/plans.ts
+++ b/src/app/plans.ts
@@ -8,12 +8,19 @@ export type PlanTask = {
 };
 
 export type PracticeItem = {
-  trackId: string;
+  trackChoices: string[];
   tasks: PlanTask[];
   dice: boolean;
   teacherNote?: string;
 };
 
+// The single track a practice item currently resolves to. Today an item always
+// has exactly one active track (the first/only one in its pool). When the dice
+// feature lands (#5), this is the seam that returns the rolled track instead.
+export function primaryTrackId(item: PracticeItem): string {
+  return item.trackChoices[0];
+}
+
 export type Plan = {
   id: string;
   createdDate: string;
diff --git a/src/app/plans/NewPlanButton.tsx b/src/app/plans/NewPlanButton.tsx
index 1a7ad3b..70d0932 100644
--- a/src/app/plans/NewPlanButton.tsx
+++ b/src/app/plans/NewPlanButton.tsx
@@ -30,7 +30,7 @@ export default function NewPlanButton({
             createdDate: today,
             description: sourcePlan.description,
             items: sourcePlan.items.map((it) => ({
-              trackId: it.trackId,
+              trackChoices: [...it.trackChoices],
               tasks: it.tasks.map((t) => ({ ...t })),
               dice: it.dice,
               teacherNote: it.teacherNote,
diff --git a/src/app/plans/PlanEditor.tsx b/src/app/plans/PlanEditor.tsx
index 8292231..f981f99 100644
--- a/src/app/plans/PlanEditor.tsx
+++ b/src/app/plans/PlanEditor.tsx
@@ -16,7 +16,7 @@ import {
   verticalListSortingStrategy,
 } from "@dnd-kit/sortable";
 import { restrictToVerticalAxis } from "@dnd-kit/modifiers";
-import type { Plan, Track } from "../plans";
+import { primaryTrackId, type Plan, type Track } from "../plans";
 import { savePlan } from "../actions";
 import { validatePlan } from "./plan-validation";
 import { nextAvailableTrackId } from "../track-id";
@@ -77,7 +77,9 @@ export default function PlanEditor({
     if (picker?.mode === "replace") {
       update({ items: replaceItemTrack(draft.items, picker.index, trackId) });
     } else {
-      update({ items: [...draft.items, { trackId, tasks: [], dice: false }] });
+      update({
+        items: [...draft.items, { trackChoices: [trackId], tasks: [], dice: false }],
+      });
     }
     setPicker(null);
   }
@@ -122,8 +124,8 @@ export default function PlanEditor({
   function handleDragEnd(event: DragEndEvent) {
     const { active, over } = event;
     if (!over || active.id === over.id) return;
-    const oldIdx = draft.items.findIndex((i) => i.trackId === active.id);
-    const newIdx = draft.items.findIndex((i) => i.trackId === over.id);
+    const oldIdx = draft.items.findIndex((i) => primaryTrackId(i) === active.id);
+    const newIdx = draft.items.findIndex((i) => primaryTrackId(i) === over.id);
     if (oldIdx === -1 || newIdx === -1) return;
     const next = [...draft.items];
     const [moved] = next.splice(oldIdx, 1);
@@ -165,16 +167,16 @@ export default function PlanEditor({
           onDragEnd={handleDragEnd}
         >
           <SortableContext
-            items={draft.items.map((i) => i.trackId)}
+            items={draft.items.map((i) => primaryTrackId(i))}
             strategy={verticalListSortingStrategy}
           >
             {draft.items.map((item, idx) => (
               <PracticeItemRow
-                key={item.trackId}
+                key={primaryTrackId(item)}
                 item={item}
-                track={trackList.find((t) => t.id === item.trackId)}
+                track={trackList.find((t) => t.id === primaryTrackId(item))}
                 disabled={disabled}
-                invalidTaskIndices={invalidByTrack.get(item.trackId) ?? new Set()}
+                invalidTaskIndices={invalidByTrack.get(primaryTrackId(item)) ?? new Set()}
                 onChange={(next) =>
                   update({
                     items: draft.items.map((it, i) => (i === idx ? next : it)),
@@ -235,7 +237,7 @@ export default function PlanEditor({
       {picker && (
         <TrackPicker
           tracks={trackList}
-          inPlan={draft.items.map((i) => i.trackId)}
+          inPlan={draft.items.map((i) => primaryTrackId(i))}
           heading={picker.mode === "replace" ? "Change track" : "Add to plan"}
           onClose={() => setPicker(null)}
           onPick={(t) => applyTrackToPlan(t.id)}
diff --git a/src/app/plans/PracticeItemRow.tsx b/src/app/plans/PracticeItemRow.tsx
index 79583ce..4139dd6 100644
--- a/src/app/plans/PracticeItemRow.tsx
+++ b/src/app/plans/PracticeItemRow.tsx
@@ -2,7 +2,7 @@
 
 import { useSortable } from "@dnd-kit/sortable";
 import { CSS } from "@dnd-kit/utilities";
-import type { PracticeItem, PlanTask, Track } from "../plans";
+import { primaryTrackId, type PracticeItem, type PlanTask, type Track } from "../plans";
 import TaskChip from "./TaskChip";
 import TeacherNoteField from "./TeacherNoteField";
 import { sortTasks } from "./task-order";
@@ -37,7 +37,7 @@ export default function PracticeItemRow({
     transform,
     transition,
     isDragging,
-  } = useSortable({ id: item.trackId, disabled });
+  } = useSortable({ id: primaryTrackId(item), disabled });
 
   const style = {
     transform: CSS.Transform.toString(transform),
@@ -58,7 +58,7 @@ export default function PracticeItemRow({
           ⠿
         </button>
         <div className="font-semibold flex-1 flex items-center gap-2">
-          <span>{track?.name ?? item.trackId}</span>
+          <span>{track?.name ?? primaryTrackId(item)}</span>
           {track && (
             <span className="text-xs bg-zinc-100 text-zinc-500 rounded px-1.5 py-0.5 font-normal">
               {track.type}
diff --git a/src/app/plans/plan-validation.test.ts b/src/app/plans/plan-validation.test.ts
index 566501d..b0342b1 100644
--- a/src/app/plans/plan-validation.test.ts
+++ b/src/app/plans/plan-validation.test.ts
@@ -9,7 +9,7 @@ function plan(items: Plan["items"]): Plan {
 describe("validatePlan", () => {
   it("returns no errors for a plan with only regular tasks", () => {
     const p = plan([
-      { trackId: "scale", tasks: [{ type: "playWithoutTrack", count: 1 }], dice: false },
+      { trackChoices: ["scale"], tasks: [{ type: "playWithoutTrack", count: 1 }], dice: false },
     ]);
     expect(validatePlan(p)).toEqual([]);
   });
@@ -17,7 +17,7 @@ describe("validatePlan", () => {
   it("returns no errors for a plan with a valid focus task", () => {
     const p = plan([
       {
-        trackId: "may-song",
+        trackChoices: ["may-song"],
         tasks: [
           { type: "playWithoutTrack", count: 1 },
           { type: "playWithoutTrack", count: 6, focus: "bars 5-8" },
@@ -31,7 +31,7 @@ describe("validatePlan", () => {
   it("flags an empty focus string", () => {
     const p = plan([
       {
-        trackId: "x",
+        trackChoices: ["x"],
         tasks: [{ type: "sing", count: 1, focus: "" }],
         dice: false,
       },
@@ -44,7 +44,7 @@ describe("validatePlan", () => {
   it("flags a whitespace-only focus string", () => {
     const p = plan([
       {
-        trackId: "x",
+        trackChoices: ["x"],
         tasks: [{ type: "sing", count: 1, focus: "   " }],
         dice: false,
       },
@@ -57,7 +57,7 @@ describe("validatePlan", () => {
   it("flags duplicate (type, focus) pairs on the same track — both offending indices", () => {
     const p = plan([
       {
-        trackId: "x",
+        trackChoices: ["x"],
         tasks: [
           { type: "playWithoutTrack", count: 6, focus: "bars 5-8" },
           { type: "playWithoutTrack", count: 4, focus: "bars 5-8" },
@@ -74,7 +74,7 @@ describe("validatePlan", () => {
   it("flags duplicate regular tasks of the same type on the same track", () => {
     const p = plan([
       {
-        trackId: "x",
+        trackChoices: ["x"],
         tasks: [
           { type: "sing", count: 1 },
           { type: "sing", count: 2 },
@@ -91,7 +91,7 @@ describe("validatePlan", () => {
   it("does not flag regular and focus tasks with the same type on the same track", () => {
     const p = plan([
       {
-        trackId: "x",
+        trackChoices: ["x"],
         tasks: [
           { type: "playWithoutTrack", count: 1 },
           { type: "playWithoutTrack", count: 6, focus: "bars 5-8" },
@@ -104,8 +104,8 @@ describe("validatePlan", () => {
 
   it("scopes duplicate detection per track — same (type, focus) across different tracks is fine", () => {
     const p = plan([
-      { trackId: "a", tasks: [{ type: "sing", count: 1 }], dice: false },
-      { trackId: "b", tasks: [{ type: "sing", count: 1 }], dice: false },
+      { trackChoices: ["a"], tasks: [{ type: "sing", count: 1 }], dice: false },
+      { trackChoices: ["b"], tasks: [{ type: "sing", count: 1 }], dice: false },
     ]);
     expect(validatePlan(p)).toEqual([]);
   });
diff --git a/src/app/plans/plan-validation.ts b/src/app/plans/plan-validation.ts
index ea1fb08..2869cc9 100644
--- a/src/app/plans/plan-validation.ts
+++ b/src/app/plans/plan-validation.ts
@@ -1,4 +1,4 @@
-import type { Plan } from "../plans";
+import { primaryTrackId, type Plan } from "../plans";
 
 export type PlanValidationError = {
   trackId: string;
@@ -9,9 +9,10 @@ export type PlanValidationError = {
 export function validatePlan(plan: Plan): PlanValidationError[] {
   const errors: PlanValidationError[] = [];
   for (const item of plan.items) {
+    const trackId = primaryTrackId(item);
     item.tasks.forEach((task, taskIndex) => {
       if (task.focus !== undefined && task.focus.trim() === "") {
-        errors.push({ trackId: item.trackId, taskIndex, reason: "empty-focus" });
+        errors.push({ trackId, taskIndex, reason: "empty-focus" });
       }
     });
 
@@ -25,7 +26,7 @@ export function validatePlan(plan: Plan): PlanValidationError[] {
     for (const indices of seen.values()) {
       if (indices.length > 1) {
         for (const taskIndex of indices) {
-          errors.push({ trackId: item.trackId, taskIndex, reason: "duplicate" });
+          errors.push({ trackId, taskIndex, reason: "duplicate" });
         }
       }
     }
diff --git a/src/app/plans/replace-item-track.test.ts b/src/app/plans/replace-item-track.test.ts
index 5e6993b..8115900 100644
--- a/src/app/plans/replace-item-track.test.ts
+++ b/src/app/plans/replace-item-track.test.ts
@@ -3,15 +3,15 @@ import type { PracticeItem } from "../plans";
 import { replaceItemTrack } from "./replace-item-track";
 
 const items: PracticeItem[] = [
-  { trackId: "a", tasks: [{ type: "sing", count: 2 }], dice: true, teacherNote: "keep me" },
-  { trackId: "b", tasks: [], dice: false },
+  { trackChoices: ["a"], tasks: [{ type: "sing", count: 2 }], dice: true, teacherNote: "keep me" },
+  { trackChoices: ["b"], tasks: [], dice: false },
 ];
 
 describe("replaceItemTrack", () => {
-  it("swaps the trackId at the index, preserving tasks/dice/teacherNote", () => {
+  it("swaps the trackChoices at the index, preserving tasks/dice/teacherNote", () => {
     const next = replaceItemTrack(items, 0, "c");
     expect(next[0]).toEqual({
-      trackId: "c",
+      trackChoices: ["c"],
       tasks: [{ type: "sing", count: 2 }],
       dice: true,
       teacherNote: "keep me",
@@ -25,7 +25,7 @@ describe("replaceItemTrack", () => {
 
   it("does not mutate the input", () => {
     const next = replaceItemTrack(items, 0, "c");
-    expect(items[0].trackId).toBe("a");
+    expect(items[0].trackChoices).toEqual(["a"]);
     expect(next).not.toBe(items);
   });
 });
diff --git a/src/app/plans/replace-item-track.ts b/src/app/plans/replace-item-track.ts
index aca2787..1b8a7b8 100644
--- a/src/app/plans/replace-item-track.ts
+++ b/src/app/plans/replace-item-track.ts
@@ -1,10 +1,13 @@
 import type { PracticeItem } from "../plans";
 
 // Swap the track on the practice item at `index`, preserving its tasks, dice, and teacher note.
+// Items hold a single-element pool until the dice feature (#5) adds multi-track editing.
 export function replaceItemTrack(
   items: PracticeItem[],
   index: number,
   trackId: string,
 ): PracticeItem[] {
-  return items.map((item, i) => (i === index ? { ...item, trackId } : item));
+  return items.map((item, i) =>
+    i === index ? { ...item, trackChoices: [trackId] } : item,
+  );
 }
diff --git a/src/app/seed-data.test.ts b/src/app/seed-data.test.ts
index 79b6b1c..db7101c 100644
--- a/src/app/seed-data.test.ts
+++ b/src/app/seed-data.test.ts
@@ -15,9 +15,11 @@ const scheduleMap = schedule as Record<string, string>;
 
 describe("committed seed data is internally consistent", () => {
   it("every plan item references a track that exists", () => {
-    for (const plan of plans as { id: string; items: { trackId: string }[] }[]) {
+    for (const plan of plans as { id: string; items: { trackChoices: string[] }[] }[]) {
       for (const item of plan.items) {
-        expect(trackIds.has(item.trackId), `plan ${plan.id} item trackId ${item.trackId}`).toBe(true);
+        for (const trackId of item.trackChoices) {
+          expect(trackIds.has(trackId), `plan ${plan.id} item trackId ${trackId}`).toBe(true);
+        }
       }
     }
   });
diff --git a/src/app/teacher-data.test.ts b/src/app/teacher-data.test.ts
index c806f6b..b192bdf 100644
--- a/src/app/teacher-data.test.ts
+++ b/src/app/teacher-data.test.ts
@@ -124,7 +124,7 @@ describe("aggregateTeacherReport", () => {
           checklist: [],
           items: [
             {
-              trackId: "twinkle",
+              trackChoices: ["twinkle"],
               dice: false,
               tasks: [
                 { type: "sing", count: 1 },
@@ -162,9 +162,9 @@ describe("aggregateTeacherReport", () => {
       schedule: { "2026-04-15": "1", "2026-04-16": "2" },
       plans: [
         { id: "1", createdDate: "2026-04-15", checklist: [], items: [
-          { trackId: "twinkle", dice: false, tasks: [{ type: "sing", count: 3 }] } ] },
+          { trackChoices: ["twinkle"], dice: false, tasks: [{ type: "sing", count: 3 }] } ] },
         { id: "2", createdDate: "2026-04-16", checklist: [], items: [
-          { trackId: "twinkle", dice: false, tasks: [{ type: "sing", count: 3 }] } ] },
+          { trackChoices: ["twinkle"], dice: false, tasks: [{ type: "sing", count: 3 }] } ] },
       ],
       tracks,
       doneByDate: { "2026-04-15": ["twinkle-sing-0", "twinkle-sing-1"] },
@@ -183,7 +183,7 @@ describe("aggregateTeacherReport", () => {
       schedule: { "2026-04-15": "1" },
       plans: [
         { id: "1", createdDate: "2026-04-15", checklist: [], items: [
-          { trackId: "scale", dice: false, tasks: [{ type: "playWithoutTrack", count: 2 }] } ] },
+          { trackChoices: ["scale"], dice: false, tasks: [{ type: "playWithoutTrack", count: 2 }] } ] },
       ],
       tracks,
       doneByDate: {},
@@ -209,7 +209,7 @@ describe("aggregateTeacherReport", () => {
       schedule: { "2026-04-15": "1" },
       plans: [
         { id: "1", createdDate: "2026-04-15", checklist: [], items: [
-          { trackId: "twinkle", dice: false, tasks: [
+          { trackChoices: ["twinkle"], dice: false, tasks: [
             { type: "playWithoutTrack", count: 2 },
             { type: "playWithoutTrack", count: 6, focus: "bars 5-8" },
           ] } ] },
@@ -233,7 +233,7 @@ describe("aggregateTeacherReport", () => {
       schedule: { "2026-04-14": "1", "2026-04-15": "1", "2026-04-16": "1" },
       plans: [
         { id: "1", createdDate: "2026-04-14", checklist: [], items: [
-          { trackId: "twinkle", dice: false, tasks: [{ type: "sing", count: 1 }] } ] },
+          { trackChoices: ["twinkle"], dice: false, tasks: [{ type: "sing", count: 1 }] } ] },
       ],
       tracks,
       doneByDate: {},
diff --git a/src/app/teacher-data.ts b/src/app/teacher-data.ts
index 4394145..58a704c 100644
--- a/src/app/teacher-data.ts
+++ b/src/app/teacher-data.ts
@@ -1,5 +1,5 @@
 import { isClassDay } from "./day-types";
-import type { Plan, PlanSchedule, Track } from "./plans";
+import { primaryTrackId, type Plan, type PlanSchedule, type Track } from "./plans";
 import { doneCountForTask } from "./task-keys";
 
 export type TeacherWindow = {
@@ -116,11 +116,12 @@ export function aggregateTeacherReport(input: AggregateInput): TrackReport[] {
     if (plan === undefined) continue; // class/sick ids never match a plan id
 
     for (const item of plan.items) {
-      if (!targets.has(item.trackId)) {
-        targets.set(item.trackId, new Map());
-        order.push(item.trackId);
+      const trackId = primaryTrackId(item);
+      if (!targets.has(trackId)) {
+        targets.set(trackId, new Map());
+        order.push(trackId);
       }
-      const byType = targets.get(item.trackId)!;
+      const byType = targets.get(trackId)!;
       for (const task of item.tasks) {
         if (task.focus !== undefined) continue; // focus tasks excluded
         byType.set(task.type, (byType.get(task.type) ?? 0) + task.count);
diff --git a/src/app/test-support/seed.ts b/src/app/test-support/seed.ts
index d5f4cd8..5425208 100644
--- a/src/app/test-support/seed.ts
+++ b/src/app/test-support/seed.ts
@@ -15,8 +15,8 @@ export const TEST_PLANS: Plan[] = [
     id: "1",
     createdDate: "2026-04-07",
     items: [
-      { trackId: "demo-a", tasks: [{ type: "playWithTrack", count: 2 }], dice: false },
-      { trackId: "demo-b", tasks: [{ type: "playWithoutTrack", count: 1 }], dice: false },
+      { trackChoices: ["demo-a"], tasks: [{ type: "playWithTrack", count: 2 }], dice: false },
+      { trackChoices: ["demo-b"], tasks: [{ type: "playWithoutTrack", count: 1 }], dice: false },
     ],
     checklist: [],
   },