I THOUGHT ATLAS WAS ONE OF THE KINGDOMS IN RWBY, BUT IT'S ACTUALLY ONE OF THE MAIN HUNTER/HUNTRESS ACADEMYS. MANTLE IS THE KINGDOM, NOT ATLAS.
So, we discovered which academy is where in today's World of Remnant video. For those of you who actually read my journals and do watch RWBY, here's what we learned:
Beacon Academy (obviously) was founded in the Kingdom of Vale.
Haven Academy was founded in the Kingdom of Mistral.
Shade Academy was founded in the Kingdom of Vacuo.
And finally, Atlas Academy was founded in the Kingdom of Mantle.
So, for those of you who thought Atlas was one of the kingdoms, have fun going back to fix that in all your fanfictions. By guys.