Ouran Koukou Host Club, Kenka Banchou Otome: Girl Beats Boys Recommendations
Both are genderbend reverse harems with a tomboyish main girl who can hold her own surrounded by rambunctious boys. Obviously Ouran is a much better series, but at 12 minutes per episode Girl Beats Boys isn't a bad watch. It's low budget but mindless fun.
If you like girls pretending to be boys, you will like both series. They are stylistically completely different, but they have a female character that has to dress up like a boy in school.