I have a 12 week old lab puppy who is really good usually but at least daily he gets in a mood where he just starts jumping and lunging at my 6 yr old and biting at him. I have tried to have my son help me with training so the dog respects him but he still is continuing with this behavior. He only does this to my son not to my husband or I, only now and then when he’s excited and playing but it’s daily to my son. Please help