Since Toddlerhood I just taught my kids "don't be a copy-cat. You know that is wrong. Think for yourself. Don't let others think for you."
They are now older and they are very good at discerning behaviors and gauging "wrongness" and they can manage themselves despite and around kids like that.
Then, in the school I work at, there is a boy that is buddies with a trouble-maker. This buddy of his was trouble since Kindergarten. And he will do, whatever his buddy does. Too. Then he gets in trouble. And then he gets miffed about it. And will lie, about what he did wrong even if he knows it was wrong. Because that is what his buddy does.
This kid is like in 3rd grade now.
He can't think on his own. He just follows.
I know the boy and his parents. They have a hard time with him. Everyday, it is some kind of issue at school and with his buddy.
I told the boy "WHY, do you just copy-cat? You know it is wrong what your friend is doing. THINK ON YOUR OWN. Tell your buddy 'I don't want to do that, I'm going to do something else...its wrong...." THINK for yourself. (he never thought of NOT doing what his friend is doing, because they are friends. I told him, so if he jumps off a cliff you are going to do that too? THINK on your own. YOU know what is wrong and right.).
And I told him, I am trying to help him. But he is older now and needs to learn that. I told the Mom too. She thanked me for telling her boy. Because he doesn't listen to them.
I see, even 5th grade boys, acting like that.
And some boys will just emulate, them. Too.
So it is something to think about.
Sure kids are kids. They act silly or do stuff.
Some mature. Some don't even if they know better.
So well, just teach your own child, about how to think for themselves and how to gauge situations and discern other kids and their own behavior and how to make, choices.
I was talking to a 5th grade boy not to long ago. Oh, he's with the cool boys who are always being "silly." Naughty. Whatever you want to call it. No, they are not "t.r.o.u.b.le. makers." But they always, are silly and causing disruptions for others. Disruptive. Being distracting. Being "funny." Boys being boys. Right? But then he gets in trouble too. And then he gets all upset, saying things like "THEY told me to.... they are all doing it too!" type thing. So I tell him, "Look, you know its wrong. Right?" (he nods his head). And I tell him "But you still do it, be one of the crowd and think its funny. But its not. Just stop it. Think for yourself. Stand up for yourself. Does being cool, mean making trouble and irritating the other kids just for fun?" (he says no). So I tell him, YOU make a choice, everyday. YOU make a choice about if you want to get in trouble or not, and see how fun that is. For yourself. Keep going. And you will keep getting reprimanded. It is a choice. You KNOW better....I know you do. Do it." Ever since then, he has been more thoughtful of his, actions and those of his other friends. He will either condone those boys "silliness" or not. And he is proud of himself. He makes, choices now. And better choices. He leads himself. Now.