No, you're right it's sexual. But it's not pervy. I look at it as a speciality. Nurses are another speciality if they're curvy. Another one is Chinese waitresses, especially if they're very cute and petite. but not Japanese (they're not so cute)IMHO. Incidentally, Japanese men are obsessed by schoolgirls (it's almost de rigeur!)
I think it's important to stress that the schoolgirl thing has become more taboo in recent years with the national obsession with 'paedophilia'. While it's right that we should be vigilant of child abusers, I think the appreciation of mature schoolgirls in uniform is a harmless past time, which has been hijacked by the sickos.
I'm sure the makers of Waterloo road know that the way the girls are portrayed is provocative and should be applauded for their honesty and for not being influenced by the squeamish prudes.
See here:
http://www.bbc.co.uk/waterlooroad/bikesheds.shtml?picture=pi cture02&type=photo#focus