diff --git a/scripts/check-progression.sh b/scripts/check-progression.sh
new file mode 100755
index 0000000..f04d929
--- /dev/null
+++ b/scripts/check-progression.sh
@@ -0,0 +1,77 @@
+#!/usr/bin/env bash
+# Usage: scripts/check-progression.sh <js|scala|fsharp>
+# Progression checkpoint: for each module N (that has tests in the track), build a temp copy where src/ holds the
+# reference solutions of modules <= N and the untouched student stubs for the rest, then run the tests of modules
+# M01..MN. All must pass: this proves a student who has finished module N has a green suite up to N, and that
+# no earlier solution secretly depends on a later one.
+set -uo pipefail
+track="${1:?usage: check-progression.sh <js|scala|fsharp>}"
+repo="$(cd "$(dirname "$0")/.." && pwd)"
+export PATH="$HOME/.dotnet:$HOME/.local/bin:$PATH"
+
+# Module -> files (relative to src/ and solutions/) that the module introduces. A directory entry copies it whole.
+# Later tasks: extend the entries for m07+ in the Scala and F# tables.
+files_for() {
+  case "$track:$1" in
+    js:01)     echo "util.js todo.js" ;;
+    js:02)     echo "model.js" ;;
+    js:03)     echo "rules.js" ;;
+    js:04)     echo "random.js spawn.js" ;;
+    js:05)     echo "game.js" ;;
+    js:06)     echo "view.js" ;;
+    js:07)     echo "io.js" ;;
+    js:08)     echo "stream.js" ;;
+    js:09)     echo "input.js app.js runtime.js browser.js main.js" ;;
+    js:10)     echo "" ;;  # edits game/input/app, already included by m05/m09
+    js:11)     echo "pong" ;;
+    scala:01)  echo "Util.scala" ;;
+    scala:02)  echo "Model.scala" ;;
+    scala:03)  echo "Rules.scala" ;;
+    scala:04)  echo "Random.scala Spawn.scala" ;;
+    scala:05)  echo "Game.scala" ;;
+    scala:06)  echo "View.scala" ;;
+    scala:07)  echo "IO.scala" ;;
+    scala:08)  echo "Stream.scala" ;;
+    scala:09)  echo "Input.scala App.scala Runtime.scala" ;;
+    scala:10)  echo "" ;;
+    scala:11)  echo "pong" ;;
+    fsharp:*)  echo "" ;;  # added by the F# tasks
+    *) echo "" ;;
+  esac
+}
+
+case "$track" in
+  js)     has() { compgen -G "$repo/js/test/m$1-*.test.js" >/dev/null; } ;;
+  scala)  has() { compgen -G "$repo/scala/test/M$1*.test.scala" >/dev/null; } ;;
+  fsharp) has() { compgen -G "$repo/fsharp/tests/M$1*.fs" >/dev/null; } ;;
+  *) echo "unknown track: $track" >&2; exit 2 ;;
+esac
+
+status=0
+for n in 01 02 03 04 05 06 07 08 09 10 11; do
+  has "$n" || continue
+  tmp="$(mktemp -d)"
+  tar -C "$repo" --exclude=.git --exclude=node_modules --exclude=bin --exclude=obj \
+      --exclude=.scala-build --exclude=.bsp --exclude=.superpowers -cf - . | tar -C "$tmp" -xf -
+  for m in 01 02 03 04 05 06 07 08 09 10 11; do
+    [ "$m" -le "$n" ] || break
+    for f in $(files_for "$m"); do
+      [ -e "$tmp/$track/solutions/$f" ] || continue   # module not (yet) present in this track
+      rm -rf "$tmp/$track/src/$f"
+      cp -r "$tmp/$track/solutions/$f" "$tmp/$track/src/$f"
+    done
+  done
+  ok=1
+  for m in 01 02 03 04 05 06 07 08 09 10 11; do
+    [ "$m" -le "$n" ] || break
+    has "$m" || continue
+    if ! out="$(cd "$tmp/$track" && ./test.sh "M$m" 2>&1)"; then
+      echo "checkpoint M$n: FAIL (M$m tests fail with solutions up to M$n)"
+      echo "$out" | tail -40
+      ok=0; status=1; break
+    fi
+  done
+  [ $ok -eq 1 ] && echo "checkpoint M$n: ok (M01..M$n pass)"
+  rm -rf "$tmp"
+done
+exit $status