My 3-year old does not strike back or even yell or move away when kids are aggressive with him, even when they hit him. I've tried roll-playing to teach him while he should never hit someone else, he also shouldn't allow kids to hit him. I've told him to push their hands away, tell them 'no, don't hit me' and move away, or tell an adult. Still, he is passive when situations arise. What am I missing??