I don't think you should blame the weed. There are so many different hobbies that people get into. To you weed helped you feel good and was your hobby, like painting to making a model car makes someone feel good. Quite different but you can see where I am coming from. I have been smoking almost every day for about 2 years straight-in 11th grade now- and I'm doing quite well in school. I don't know why you blame weed for making you do bad in school? Why can't you enjoy it and do your work man, it really is not that hard. You made yourself like that, not the weed. It is all about your attitude. Don't try to scapegoat and you will find peace.

I hope I've helped you, I don't mean to sound like a dick.