How do you prevent your child from picking up bad behaviors from his/her playmates?

Hi, You will have to tell him that what he has picked is bad. And should tell him that he should tell his friend as well that it is not nice and he should not do it. You will have to constantly tell your child when he repeats something and can encourage him when he doesn't do that. You can love him, hug him even treat him if he complies to your directions. Also, you can speak to the teacher in the lass or daycare so that she addresses the thing. When teacher says something, children have more impact of it.