diff --git a/docs/testing.md b/docs/testing.md
index 29bf1d4..fb00509 100644
--- a/docs/testing.md
+++ b/docs/testing.md
@@ -38,6 +38,8 @@ into separate layer-shell windows.
 - [ ] Fullscreen YouTube video uses the whole display
 - [ ] Leaving fullscreen restores the correct geometry above the dock
 - [ ] No first-run, default-browser or sign-in nag appears
+- [ ] `chrome://policy` lists the Ekklesia policies as applied, with no
+      "unknown policy" entries
 - [ ] Chrome does not start by itself at boot
 - [ ] After a reboot, cookies and site logins are still there
 - [ ] After an OTA update, cookies and site logins are still there
diff --git a/scripts/classroom-window b/scripts/classroom-window
index 9d7a75c..81d5363 100755
--- a/scripts/classroom-window
+++ b/scripts/classroom-window
@@ -18,6 +18,11 @@ import sys
 
 HIDDEN_WORKSPACE = "__ekklesia_hidden"
 
+# sway parks scratchpad windows on a workspace of its own. Nothing here
+# puts them there, but treating it as hidden means a window left in the
+# scratchpad by an older classroom build can still be restored.
+HIDDEN_WORKSPACES = {HIDDEN_WORKSPACE, "__i3_scratch"}
+
 STATE_DIR = os.path.join(
     os.environ.get("XDG_RUNTIME_DIR") or "/tmp",
     "ekklesia-classroom",
@@ -77,7 +82,7 @@ def collect(node, workspace, found):
                 "instance": properties.get("instance") or "",
                 "focused": bool(node.get("focused")),
                 "workspace": workspace,
-                "hidden": workspace == HIDDEN_WORKSPACE,
+                "hidden": workspace in HIDDEN_WORKSPACES,
             }
         )
 
@@ -119,11 +124,11 @@ def visible_workspace():
     workspaces = query("get_workspaces") or []
 
     for workspace in workspaces:
-        if workspace.get("focused") and workspace.get("name") != HIDDEN_WORKSPACE:
+        if workspace.get("focused") and workspace.get("name") not in HIDDEN_WORKSPACES:
             return workspace.get("name")
 
     for workspace in workspaces:
-        if workspace.get("visible") and workspace.get("name") != HIDDEN_WORKSPACE:
+        if workspace.get("visible") and workspace.get("name") not in HIDDEN_WORKSPACES:
             return workspace.get("name")
 
     return "1"