Hey! Im also 14! dont worry so much about balancing girls and school. Im a girl. Personaly I like guys that are smart and work hard in school. Just do some of both things, but remember that your school work is equaly if not more important than your love life, and if the girls you know cant apriciate that then they're not the kind you should be going out with. So just dont worry!
and dont worry about girls not saying yes when you ask them out. If they know you and you talk to her and she seems to like you then she will most likely say yes. if she doesnt then just move on.