Film school can give you the reason to spend tons of time studying film making, but will not guarantee that you know anything when you graduate. People who take the time to study on their own can get alot out of school, because they get access to gear and some learning structure with projects, etc.
Most of the people I went to film school with were not as interested in reading/studying and as a result I don't think they learned much. For some reason, a lot of people go to film school and think that they already know more about everything than the teachers, so they pretty much just waste their time.
Soo, if you already know it all (atleast in your own mind) don't bother with school. If you are willing to listen to some hasbeen recount their extremely limited (though still valuable) experience, and try things that make you uncomfortable or are not directly linked to your interests school can be invaluable.
I went to the LA film school and got a pretty good overview, and enough experience to get my bearing and start chasing "the dream." However I also got a big student loan payment as well.