R.,
It is so hard to say. My little older daughter used to do anything but her school work. I was reemed by her second grade teacher because the teacher knew her abilities, but she did not always perform. She told me my daughter would crawl under the desk, act out, disrupt, etc. I was shocked that was my daughters behavior since I felt she was not raised that way. Sometimes she would do so good reading and sometimes she would screw off. Sometimes she could stay within the lines when writing sentences and some times she wrote right down the side of the paper.
That summer, I took her in for photos and the photographer had so much fun with her, he kept shooting and flashing the lights on her. Well in the photos, one eye took off to the left while the other stayed in place. She had a lazy eye. It wasn't apparent until she was really tired.
As it turned out, her eye would get tired and she couldn't see. The doctor (below) told me to have her sit at the front of the class because it was too much work on her eyes to look at the board from a distance and then down on lined paper and back up as they wrote sentences. So when she couldn't do it anymore, she screwed off, or just wrote down the side of her paper. I would have never thought!
I took her to a great doctor here in Vegas Dr. Mary Carroll who is considering retirement, but she did 24 weeks of eye therapy with her and her eye did a lot better without the surgery. She is an adult now and she doesn't seem to have these problems. In fact, it actually increased her hand eye coordination like you wouldn't believe. Now my baby has a little lazy eye. I have to get her in to see her before she retires on me.
Best of luck. Just watch you little guy for any signs of things that could distract him or make him give up and just day dream.