firstly we should make understand them the importance of education and studies,then we should be polite to them and hear their problems and also try to solve out them if he/she understand by this than it is good but if they don't understand after lot of explanation try to ignore him/her and tell them that if they don't want to study its ok but let others study and be quite in class.if then also that guy act like this hand over him/her to teacher and let the teacher solve this problem.