I don't see the point of expelling a fourth-grader and seeking criminal charges against him. But, with the nanny-state idiocy we have now, warming the seat of his britches, as should be done, will get you charged with child abuse and if the school does it will get them sued by the parents and charged.
Had I done something like that when I was in the fourth grade (and we won't talk about how long ago that was), I'd still be eating my supper standing up!! The principal would have warmed my backsides up, then Mom would have had a go, and, finally, Dad would have put the finishing touches on. First would have been the paddle at school, then Mom's switch (she couldn't use a belt, which is a hilarious story), and then Dad's belt.
Yes, I am the voice of experience on that. No, I won't tell you what I did, but I will tell you that I didn't do it again!!!