It is so hard watching them be mean to other children! My oldest will be 5 next month and she really takes a leadership role and the playground and sometimes she excludes some of the others. It is really hard to watch and respond appropriately to. I usually just call her aside and tell her she should try to be nice to everyone. Sometimes this works (usually) and sometimes it doesnt. If it doesn't I usually end up getting disgusted with her and taking us home.