Why is my son behaviour good in school but bad at home?

The child is the same, so there is a difference in the way you treat him and the teacher treats him. My view is the opposite of the other people, because I have seen the way parents often treat children. They do not make time for their own children, but just order them around. 

His teacher praises him, so he does well. I wonder if you raise your voice, shout at him, order him about and talk down to him. If so, talk gently and praise him for doing well. Take a real interest in what he is doing, let him show you his homework and talk about things in his life. 

You have lost control of your child.  His behavior has not been corrected, he is behaving the way he has been allowed to behave.  He has dominated you & you have allowed it.

To bad we cannot even punish our kids the way we were disciplined as children.  I learned respect for my mom cause she reinforced her rules.  We can't do that these days so the kids go wild.

Sounds like you do not demand proper behavious and/or respect at home.