To be honest, in school, there’s not much to do; you can raise your value relative to classmates by AMOGing them, build Preselection by sitting with female friends at lunch, pass notes, display intelligence, have instant-dates, and get wonderful gaming opportunities. Besides all of that, though, it's not great.
As far as talking to girls goes—school is not the best place: you have only a few minutes in between classes, maybe some time during a break or study hall, and lunch. Do not make game your priority at school; make school your priority. Seriously, pay attention in class.
Exceptions include: if some other guy starts acting up or trying to crack jokes, AMOG him; if there's a new girl, talk to her and maybe use some Transferred Kino; if you have some free time, open a set, tell some stories, and kino. In school, people yearn for fun; if you get an appropriate chance, give it to them.
Other In-School pointers include:
Beware: while gaming in school is very easy, it may lead to extremely troubling complications. Proceed with caution. I try not to game in school for the simple reason that interactions may get messy and lead to gossip—our number one enemy.