My son has picked up some abuses from kids in his school and casually uses them in conversations. Ive tried scolding him and trying to make him understand its not right but he continues. My wife and me are worried, how do I break this habit?

First you need to check the root cause of this problem, When children use abuse words, they may not understand what the words mean literally: Explain the kid about the real meaning of the abuse words and how it affect others internally. Also tell some stories to make him/her understand that this is not a good habit. Meet the school teacher and discuss the problem to fix it quickly. Literal: Which character or habit that you cannot change at 5 years old you won't be able to change at 50 years old. So parents need to take care of your kids.