Which is the chicken and which is the egg?

With the current culture of no bullying it seems to me that bullying is still happening at an alarming rate. I'm sorry your son is being bullied. Have you spoken to his teachers and asked them to observe the situation? Maybe if your son knew his teachers were watching he would feel empowered even if he doesn't retaliate. If it escalates after speaking with the teachers make an appointment with the school administrator. Often an involved parent helps the overall situation. Prayers for wisdom as his mother and for the safety of your son.