Depending on context, school girl can be a fangirl who gets shy around boys but totally chipper with her friends. Typically, a school girl likes to wear plaid skirts, ponytails or braids, a blouse or a turtleneck, long socks, and maryjane styled shoes. Sometimes black nerdy glasses and/or bubblegum make their accesory.
School Girl 1: Oh my gosh, did you see Jason? He is sooo cute! OHMYGOSH, he's coming this way! I get so school girl around him!
School girl 2: Me too! He's sooo mysterious!