Such behaviors can be managed by some sraightforward limit setting at the school. If your son is otherwise normal ,he should respond to limit setting fine. Five-year-olds aren't famous for sustained attention and they normally require supervision and monitoring to stay on task. Not having evaluated your son, I won't venture to say why he might be doing what he is doing ,but her certainly requires some systematic management of the behavior by the personnel at school.
Thanks-you are absolutely right-I just needed to be reminded that 5 yrs olds aren't famous for sustained attention and the management of his behavior is what I intend to address with the teacher.