I'm not sure if you want your Construct files to be playable in a browser or just available for download, but my suggestion would be to host everything through Google Classroom and have your students join this. That way, you have complete control over the project and can also upload, embed or link to any supporting documents. If you want a version of the game playable in a browser, I suppose you could host it through a private itch.io page which is only accessible through a specific link. Hope this helps!