The teachers at Chidori are great for fostering a welcoming atmosphere where even nerds and jocks can be friends. Sure, they're far from the best at producing lots of academically excellent students, but it seems at least their students' hearts are in the right place. And as Saku demonstrates, not everybody in that school is a certified idiot. There are intelligent students there too, and some probably go there simply because they can't afford to go to a private school, although I've yet to see an actually poor character in this story, since the boys and Kaoruko all seem to be firmly middle class.
Maybe Saku can make up with that other guy some day as part of a continuation of his story, but for now it's enough to get his point across to Ayumi.