Maybe they can relate to the primarily female cast?

They get half nude in front of most male teachers, too?

Nonthreatening, adorable male lead maybe. And judging from what I've seen at clearly male-biased sites, shoujo manga seems to trade in sexy stuffs as or more explicitly than boy's manga, even, so it's not like the kind of near-fucking you get in Negima's more pandering chapters would be completely alienating and unwelcome.