It's all you, you can do it if you really really want to, you just don't. I have the same problem. I'm a relatively smart kid, usually know what I'm talking about, I don't act black or anything, I just have shitty fucking grades, which I thought I was going to bring back up but I never did. I can learn anything interesting. I think our problem is more common than you think. I've seen smart people stupid as fuck, and stupid people telling me what's up. It just depends on you and if you want to do it. All I can really say is, keep trying, read about school stuff on wikipedia or something. You can do it, I know you can, you just don't want to. I've also experienced being more capable of concentrating when high. I've seen people drive better high. Now if you will excuse me, I'm going to go take some bong rips.