Baka and Test:Summon the Beats is a HILARIOUS animê that involves a lovable idiot named Akihisa Yoshii and his friends in Fumizuki Academy; a school that divides their students in classes (A to F) por their scores on a special test that basically judges how smart they are. At Fumizuki Academy all the students can summon "avatars" chibi versions of themselves that gain power from how high their student's test scores. I won't explain it all. Just watch it, it is great.
Clannad, Lucky Star, The Melancholy of Haruhi Suzumiya, Full Metal Panic, Heaven's lost Property, The Familiar of Zero, Shuffle, and K-On. Those are the only ones I've seen (besides rosario vampire) that match both your criteria.
A Certain Magical Index and Is this a Zombie? both are action comedies where the main character is a high school student, but school isn't considered one of the genres.