My son was superior in all school activities and even in personal activities also. In recent times I came to know that he steals lunch of other students and sometimes books and pen also. The school teachers complained me for all these things. When I scold him he turns into bad boy and he tries to break the window glasses and crockery items. Please help me out to solve this problem.
Huhhhh.. Seriously it is a very strange problem. As you said your son was good in studies and extracurricular activities but he has been changed from last some time. It is possible that your son is struggling with some psychological issues. You need to have close and friendly conversation with your son first.
Some of the time teenagers suddenly started to show unnecessary changed behavior. It is because of changes in their hormonal growth. This is not a mental distress. Your son just requires your extra care and attention right now. Your guidance can bring him back to his old track.
I think your son is suffering from unmanageable anger problem. As you said that he was brilliant in his studies and personal activities also. But suddenly he got changed and now he behaves very rudely. You can make him understand and tell him that all these activities are not good for him.
Sometimes children behaves very rudely due to some family problems, break-off with his girlfriend and physical problems. You can take the prescription for your son from any inpatient treatment centers. In these centers, special experts give the treatment and your son will definitely get well soon.