diff --git a/src/stories/hubbles_law/database.ts b/src/stories/hubbles_law/database.ts
index 5cfeb1b..697b95f 100644
--- a/src/stories/hubbles_law/database.ts
+++ b/src/stories/hubbles_law/database.ts
@@ -367,22 +367,50 @@ export async function getClassMeasurements(studentID: number,
 
 // The advantage of this over the function above is that it saves bandwidth,
 // since we aren't sending the data itself.
-// This is intended to be used with cases where we need to frequently check the class size,
-// e.g. the beginning of stage 4 in the Hubble story
+// This is intended to be used with cases where we need to frequently check the number of measurements
 export async function getClassMeasurementCount(studentID: number,
                                                classID: number | null,
                                                excludeWithNull: boolean = false,
 ): Promise<number> {
-    const cls = classID !== null ? await findClassById(classID) : null;
-    const asyncClass = cls?.asynchronous ?? true;
-    let data: HubbleMeasurement[] | null;
-    console.log(classID, asyncClass);
-    if (classID === null || asyncClass) {
-      data = await getHubbleMeasurementsForAsyncStudent(studentID, classID, excludeWithNull);
+  const cls = classID !== null ? await findClassById(classID) : null;
+  const asyncClass = cls?.asynchronous ?? true;
+  let data: HubbleMeasurement[] | null;
+  if (classID === null || asyncClass) {
+    data = await getHubbleMeasurementsForAsyncStudent(studentID, classID, excludeWithNull);
+  } else {
+    data = await getHubbleMeasurementsForSyncStudent(studentID, classID, excludeWithNull);
+  }
+  return data?.length ?? 0;
+}
+
+// Similar to the function above, this is intended for cases where we need to frequently check
+// how many students have completed their measurements, such as the beginning of Stage 4 in the Hubble story
+export async function getStudentsWithCompleteMeasurementsCount(studentID: number,
+                                                               classID: number | null,
+): Promise<number> {
+  const cls = classID !== null ? await findClassById(classID) : null;
+  const asyncClass = cls?.asynchronous ?? true;
+  let data: HubbleMeasurement[] | null;
+  if (classID === null || asyncClass) {
+    data = await getHubbleMeasurementsForAsyncStudent(studentID, classID, true);
+  } else {
+    data = await getHubbleMeasurementsForSyncStudent(studentID, classID, true);
+  }
+  const counts: Record<number, number> = {};
+  data?.forEach(measurement => {
+    if (measurement.student_id in counts) {
+      counts[measurement.student_id] += 1;
     } else {
-      data = await getHubbleMeasurementsForSyncStudent(studentID, classID, excludeWithNull);
+      counts[measurement.student_id] = 1;
     }
-    return data?.length ?? 0;
+  });
+  let num = 0;
+  for (const id in counts) {
+    if (counts[id] >= 5) {
+      num += 1;
+    }
+  }
+  return num;
 }
 
 async function getHubbleStudentDataForAsyncStudent(studentID: number, classID: number | null): Promise<HubbleStudentData[] | null> {
diff --git a/src/stories/hubbles_law/router.ts b/src/stories/hubbles_law/router.ts
index 46783c4..61c6761 100644
--- a/src/stories/hubbles_law/router.ts
+++ b/src/stories/hubbles_law/router.ts
@@ -33,7 +33,8 @@ import {
   removeSampleHubbleMeasurement,
   getAllNthSampleHubbleMeasurements,
   tryToMergeClass,
-  getClassMeasurementCount
+  getClassMeasurementCount,
+  getStudentsWithCompleteMeasurementsCount
 } from "./database";
 
 import { 
@@ -284,10 +285,41 @@ router.get("/class-measurements/size/:studentID/:classID", async (req, res) => {
   const count = await getClassMeasurementCount(studentID, classID, completeOnly);
   res.status(200).json({
     student_id: studentID,
+    class_id: classID,
     measurement_count: count,
   });
 });
 
+router.get("/class-measurements/students-completed/:studentID/:classID", async (req, res) => {
+  res.header("Cache-Control", "no-cache, no-store, must-revalidate");  // HTTP 1.1
+  res.header("Pragma", "no-cache");  // HTTP 1.0
+  res.header("Expires", "0");  // Proxies
+  const studentID = parseInt(req.params.studentID);
+  const isValidStudent = (await findStudentById(studentID)) !== null;
+  if (!isValidStudent) {
+    res.status(404).json({
+      message: "Invalid student ID",
+    });
+    return;
+  }
+
+  const classID = parseInt(req.params.classID);
+  const isValidClass = (await findClassById(classID)) !== null;
+  if (!isValidClass) {
+    res.status(404).json({
+      message: "Invalid class ID",
+    });
+    return;
+  }
+
+  const count = await getStudentsWithCompleteMeasurementsCount(studentID, classID);
+  res.status(200).json({
+    student_id: studentID,
+    class_id: classID,
+    students_completed_measurements: count,
+  });
+});
+
 router.get(["/class-measurements/:studentID/:classID", "/stage-3-data/:studentID/:classID"], async (req, res) => {
   const lastCheckedStr = req.query.last_checked as string;
   let lastChecked: number | null = parseInt(lastCheckedStr);