As far as I can tell, Balamb started in order to train Squall and the others to defeat the Sorceress, because Squall is the one who came from the future and convinced Edea that he was the one to do it, so the training is more strict, I suppose? Tribia and Galbadia also train SeeD but they don't have the guy who started this whole thing so maybe they're a bit more lax?

Meaning, maybe Balamb's attitude is more "Go, go, go, we know Squall is the one who's supposed to defeat the Sorceress. Exercise should be done through training and fighting monsters."

And the other two don't have Squall so they add extra rec activities for their students?

I dunno.