A.F.
A.,
My best advice would be to have the school do a "time on task" assessment to evaluate how much time he is able to focus. A school psychologist is usually the one to do this although the school counselor can do it too. My oldest son (10) has struggled with the same problems and others ever since he was in Kindergarten. His original "time on task" was done when he was in 1st grade and we were told he was fine. His behavior/problems continued and finally when he was in 3rd grade we had him professionally evaluated outside the school. He was diagnosed with ADD.
I am certainly not saying that your son has this as well and it was not a diagnosis that was made without thorough screening by several doctors (pediatrician, psychiatrist, psychologist). The "time on task" is not a sure fire way to evaluate your son but it is the best first step to take with trying to help him. If the test comes back fine just keep watching him and keep in good contact with his teacher. We have found that email works great for this.
If he continues to struggle, talk to his pediatrician to see if he/she has a referral to a reputible place to have him screened further. Some pediatricans are quick to just hand out meds. Please, for your son's sake, have him professionally evaluated before going that route.
Some things that have helped my son stay a bit more focused at school are having his seat closest to the teachers desk and close to the front of class.
I hope this helps and I pray that you will find what you need to help him. :)