be friends with?

be friends with?be friendly with 与某人友好be friends with 做题时遇到这么一句话：You have to be friends with your pupils and take good care of them……难道是印刷错误?这是一道改错题阿郁闷（错误不是friends这一块,我改的这一块,人家答案改得别的地方……）那我要是把它改成be friendly with 能算对吗