What 2 Learn has a variety of templates, and a fairly easy process, that teachers and students can use to create learning games.
I wouldn’t say it’s quite good enough to be added to my The Best Websites For Creating Online Games, but it’s certainly worth a look.
(Note: Teacher Lauren Allsop in the comments section thinks more highly of What 2 Learn than I do. I guess I’ll take a second look.)
I’ve placed the link on my website under Student Video Games.