kids diet

ok long story short my son has behavior problems at school like bad ones he's in 3rd grease this has happened since kindergarten we have tried every time in and time out you an yhink.of I've whooped his but, counseling, reward systems nothing has worked he's been tested for add/adhd I guess he's not. I'm clueless yesterday I was looking up different ways to handle behavior problems and came across a no dye gluten free diet has anyone at all tried this for a child with behavior problems