I don't think, the academy was built in the purpose of teaching the monters how to live with humans in the human "world" after graduating. Everyone will return.
I don't really remember to the barrier of Yuki-Onna village but I remember to a human boy there.. Maybe there are more youkai villages in the world it would be hardly enough to every monster (and of course tsukune doesn't have his "own" village to live in, he has a family and many-many girlfriends who wish to live with him
they will able to defend his family and it's only a matter of time when the secret is going to be revealed..)
An other option is to buy a house and live seperately from his family.