Close.

[But then, he'd tossed out quite a few possibilities there.]

...It's a school where animal spirits can learn to transform into and blend in with humans. The barrier keeps them inside so they don't run into humans until they're ready, and it keeps humans out so they don't run into the animals.

[That, and... protects humans from any animals with bad intentions who haven't been weeded out yet.]

I'm not... sure why all of you appear like that, though.