My hair is so oily and greasy and i have to wash it every two days!! What can i do?

hey everyone. Well im 14 now so i hit puberty. The thing is that my hair has been really oily for some months and it really gets on my nerves because i have to wash it every two days.....so any remedies?? I tried so many shampoos but none of them did what they said they would do. And that kinda sucks i mean my mum doesnt even agree with the idea of washing my hair everyday coz she says ill end up washing it every day and sometimes i have to go to school with my sucky hair....its not a matter of money...its just that she doesnt want me to emd up washing my hair 7 times a week lol. So..can u think of any things that might heelp thanks?