I can't quite be myself at home?

I am a very random, funny, and cool person - at school. Recently I had kind of a personality change, I used to be a know-it-all teacher suck-up, but now I'm more relaxed and funny, but I still get good grades. I have a variaty of interests, and one of my main ones is acting. I really want to be am actor, but my family doesn't have much money, and my mom doesn't think I should be. More importantly, my mom still thinks I have my old personality. I'm mor relaxed at home, but she doesn't really understand me. There's stuff like t-shirts that I want to get that she frowns upon. I just really want to be myself, but I'm afraid of hurting her. I want to pursue acting, but my mom thinks I'm too young. I have almost a conpletly different life at school, and I really like it, and so do my friends. If my friends come over, I have to act different. What should I do?