Well when you have heard that each person has a different personality and he or she acts according to it. You can't ask a revolution er to meditate. Why because his job and nature is belonging to rebellion. Moreover a saint can't take up his job so just like this some children are rebellious and should be handed like kid gloves while docile ones need a crisp word. As for bad grades a car does not always runs on a smooth track even can not make mountains without valleys between them.