Why Math only? How can i improve?

Well, to start off, I'm a pretty good student. I take advanced courses (by one grade level) and i get good grades in other subjects. I'm a wiz at science, language arts and world history and the rest of my religion topics. But i lose it in Math. During Math cl, i don't notice, but my teacher yells at me for often gazing off. I'm only in eighth grade and am worried about my future. This quarter i got all A's and B's except math. I normally fail all my tests and quizzes. During cl i think i get it, but when i go home and solve my homework problems i usually miss all. Next year I'm moving on to high school and i need to get good grades. I need some good study tips, something that will help me stay focused and actually know what the teacher is talking about.