1)pay attentive in class especially in math as you can't learn by yourself without a teacher help.If you are getting distracted by your friends or enemies sit in the first bench or any place where you won't get distracted.
2))do all the sums which was done in the class.if u don't understand ask a teacher(no offense but there are few teachers who won't solve doubts.so if u want to know urgently you can mail me anytime).
3)do your hw .Its one of the basic problem that all children doesn't do math well,if u do your homework you would get to know your mistakes
4)submit your assignment on time,class works,etc.so that the teacher can get to know your mistakes.
5)these steps would gurantee you 85% or above in math.trust me