Is there any reason he would feel protective towards her, has he experienced any abuse towards her or negative behavior. Is his Dad in the picture? His Mom is the one who can solve this behavior pattern by being firm and strong,and not giving way, reasuring him she is okay ,and other esteem building remarks., tell her to give him plenty of time in the morning to get ready and have breakfast with her , children hate being rushed around , very often that morning race to school becomes a nightmare of yelling!! Good luck