School, university, and prison are all institutions. Stay in school, go to university, stay out of prison. You don't go to store though, hang out at mall, meet

School, university, and prison are all institutions. Stay in school, go to university, stay out of prison. You don't go to store though, hang out at mall, meet at restaurant, or go to bar for a drink. I think the difference between the two usages is considering "hospital" an institution. I also don't think a vs the requires the listener to know which specific place you're talking about, it seems to also communicate that the speaker knows what place they're talking about. "I'm going to the store to buy carrots" vs "I'm going to a store to buy carrots." Someone knows vs no one knows.