It is a life sim, it is about doing what you want to do and interacting with the npc's in it. Many have story arc's you just have to get to know them and talk to them first.
Well if you picked school girl regardless which one then i suggest getting to know your fellow students at school, at the disco and some hang out at the beach on the weekends and warm days, and then some around the apartment complex to just get their relationships up, until it starts unlocking their story.
here is a rough guide to the school npc's and how much content they have. I have not done all the stories in awhile so some of them might have more than is listed.