How can we teach?.

This is a big broblem.

I will tell one incident.
One of my friends son is 12 years. He is always telling lies. the small things like hiding his class test papers, not attending class and not lessioning, not respecting etc. even last week his father was abset because he got very low marks in his class test but he shown him the other classmate paper as his paper because that boy got high marks.

Please note:- they are not beating their son, some time they shout that's all.
Last two months they talk with him, and want to find the broblem but it is failure.

Now, advice me how to handle this kind of child

Teach them love and not hate..