my son is 3.1 years. but his weight is just 11kg. don't know why? he is very stubborn n never listen to me. now from some days he has started hitting everyone. I m a teacher by profession. so it is very necessary to make my child a sincere n disciplined child. but doesn't understand if I learn him what is bad n good for him. what should I do. because this is the age when he can learn good n bad.