can my school check up on me on facebook? and reprimand me for saying school is stupid on there
Basically, yes.
You just learned a very valuable lesson. Be careful what you post. It is public & it remains on the internet forever.
People are reading things I've posted 10 years ago! The internet has a long lifespan.
Plus employers & colleges read what you post! People are not getting accepted to colleges & are losing job offers because of things they post.