7 years old behavioral problem

My son is 7 years old and in first grade, he has all A and B+, but he has trouble following the teachers instructions. For example if there is a test he will finish it before the teacher gives the instructions and most of the time he gets it right, but if the instructions were to circle and he underlines it he is going to have it wrong because he didn't follow instructions. He always has to be the first in everything, sometime I punish him by telling that his sister is going to choose first and that really hurts him. What can I do to help him follow instructions and behave in school? The teacher is worried that he might have ADD.

[tinkerbell1124]

It's possible he could have ADHD or ADD. It may just mean he's bored and NOT being challenged enough. And maybe take a little more time with him when the HE ALWAYS wants to be first come up. Explain to him more about WHY he can't always be first. That everyone deserves a turn to be first.