diff --git a/bin/mark-class-projects.lua b/bin/mark-class-projects.lua
new file mode 100644
index 00000000..1f03a153
--- /dev/null
+++ b/bin/mark-class-projects.lua
@@ -0,0 +1,140 @@
+-- Mark class projects utility
+-- ===========================
+--
+-- Sets likely_class_work = true on a user's projects, or on a single
+-- project, and propagates the flag to all (transitive) remixes.
+--
+-- Not meant to be used from Lapis but as a command-line utility.
+-- Reads database connection details from the same env vars used by
+-- bin/migrate.lua and config.lua.
+--
+-- Usage:
+--   lua bin/mark-class-projects.lua --user <username>
+--   lua bin/mark-class-projects.lua --project <project_id>
+--
+-- Copyright (C) 2026 by Bernat Romagosa and Michael Ball
+--
+-- This file is part of Snap Cloud.
+--
+-- Snap Cloud is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU Affero General Public License as
+-- published by the Free Software Foundation, either version 3 of
+-- the License, or (at your option) any later version.
+
+local pgmoon = require('pgmoon')
+
+local usage = [[
+Usage:
+  lua bin/mark-class-projects.lua --user <username>
+  lua bin/mark-class-projects.lua --project <project_id>
+]]
+
+local mode, value
+local i = 1
+while i <= #arg do
+    local a = arg[i]
+    if a == '--user' or a == '-u' then
+        mode = 'user'
+        value = arg[i + 1]
+        i = i + 2
+    elseif a == '--project' or a == '-p' then
+        mode = 'project'
+        value = arg[i + 1]
+        i = i + 2
+    elseif a == '--help' or a == '-h' then
+        print(usage)
+        os.exit(0)
+    else
+        print('Unknown argument: ' .. tostring(a))
+        print(usage)
+        os.exit(1)
+    end
+end
+
+if not mode or not value or value == '' then
+    print(usage)
+    os.exit(1)
+end
+
+if mode == 'project' then
+    value = tonumber(value)
+    if not value then
+        print('--project expects a numeric project id')
+        os.exit(1)
+    end
+end
+
+local db = pgmoon.new({
+    host = os.getenv('DATABASE_HOST') or '127.0.0.1',
+    port = os.getenv('DATABASE_PORT') or '5432',
+    database = os.getenv('DATABASE_NAME') or 'snapcloud',
+    user = os.getenv('DATABASE_USERNAME') or 'cloud',
+    password = os.getenv('DATABASE_PASSWORD') or 'snap-cloud-password'
+})
+
+assert(db:connect())
+
+-- Build the seed set: projects we are explicitly marking as class work.
+local seed_query
+if mode == 'user' then
+    seed_query =
+        'SELECT id FROM projects WHERE username = ' ..
+            db:escape_literal(value)
+else
+    seed_query =
+        'SELECT id FROM projects WHERE id = ' ..
+            db:escape_literal(value)
+end
+
+-- Mark seed projects, then walk the remix tree marking every descendant.
+-- The recursive CTE follows remixes.original_project_id -> remixed_project_id,
+-- so a remix of a remix of a seed is also caught.
+local update_sql = [[
+WITH RECURSIVE seed AS (
+    ]] .. seed_query .. [[
+
+),
+descendants AS (
+    SELECT id FROM seed
+    UNION
+    SELECT r.remixed_project_id
+    FROM remixes r
+    INNER JOIN descendants d ON d.id = r.original_project_id
+)
+UPDATE projects
+SET likely_class_work = true
+WHERE id IN (SELECT id FROM descendants)
+  AND likely_class_work = false
+RETURNING id
+]]
+
+local result, err = db:query(update_sql)
+if not result then
+    print('Update failed: ' .. tostring(err))
+    os.exit(1)
+end
+
+local updated = #result
+local seed_result, seed_err = db:query(seed_query)
+if not seed_result then
+    print('Could not count seed projects: ' .. tostring(seed_err))
+    os.exit(1)
+end
+
+if mode == 'user' then
+    print(
+        'User ' .. value .. ': ' .. #seed_result ..
+            ' owned project(s); ' .. updated ..
+            ' project(s) newly marked likely_class_work=true ' ..
+            '(including remix descendants).'
+    )
+else
+    if #seed_result == 0 then
+        print('No project found with id ' .. value)
+        os.exit(1)
+    end
+    print(
+        'Project ' .. value .. ' and its remix descendants: ' ..
+            updated .. ' project(s) newly marked likely_class_work=true.'
+    )
+end
diff --git a/controllers/project.lua b/controllers/project.lua
index 911583dc..3c43d1fe 100644
--- a/controllers/project.lua
+++ b/controllers/project.lua
@@ -445,6 +445,14 @@ ProjectController = {
                 remixed_project_id = self.params.id,
                 created = self.params.created
             })
+            if original_project.likely_class_work then
+                local remixed_project =
+                    Projects:find({ id = self.params.id })
+                if remixed_project
+                        and not remixed_project.likely_class_work then
+                    remixed_project:update({ likely_class_work = true })
+                end
+            end
         end
 
         return okResponse()
@@ -619,6 +627,13 @@ ProjectController = {
 
             local likely_class_work = self.current_user:is_student() or
                 is_likely_course_work(self.params.projectname)
+            if (body.remixID and body.remixID ~= cjson.null) then
+                local original_project =
+                    Projects:find({ id = body.remixID })
+                if original_project and original_project.likely_class_work then
+                    likely_class_work = true
+                end
+            end
             Projects:create({
                 projectname = tostring(self.params.projectname),
                 username = tostring(self.params.username),