Ferris Bueller's Day Off is probably the funniest film of the John Hughes era.
Juno is very good, though I suppose it's not technically a "high school" movie, despite having a high school setting and characters of high school age and... okay fine, it's a high school movie.
Napoleon Dynamite is the best G-Rated Comedy of all time (in Canada it's G, PG in the states)
characters or issues in that one (never did drugs, was a nerd)
I personally HATED Dazed and Confused but mostly because I couldn't relate to any of the
Brick is the best movie about High School ever. It's funny, but not for the reasons you would expect, in fact, it's actually pretty dark.