Behaviour Problem. I am not sure.

My son,age 7,class 3. He is good in studies but don't want to study, he gets gud grades in class coz his mother teaches him although he don't want to study. He have good grasping power but don't want to concentrate. But this is not the real problem. The real problem is that he don't listen to anybody regarding any matter. When someone say "YOU SHOULD NOT DO THIS" he just simply ignore.he just don't give a damn. Today night he was playing with his younger brother who is of 2.5 years of age & he accidentally hit his eye, it was a deep injury & the younger one was crying continually & on the other hand he didn't had any regret for that instead while everyone was trying to stop the younger one from crying, he was continuously demanding for one or the other thing. His class teacher always complains that he is good in studies but he talks too much. He have been instructed to talk less but he don't follow us & just ignore us. I don't know what's the problem with him. Whom should i see ?