soiling 8 year old

I didn't know where to post this. My eight year old son has been soiling himself at school for the past 4 days. He will hold his bowels while everyone has the bathroom break and then "go" on himself in the afternoon. He does have control of his bowels. We were having trouble getting him to do his work in the past. Now, he does his work and his teacher says he is not a behavior problem. I just don't know what could be going on. No type of dicipline seems to get him to stop. We are a loving and very close family. He gets plenty of attention. I could use any advise. Thanks in advance.