The first approach is to give LOTS of Grace and Courtesy lessons— every day if needed, at least several each week.

If the negative behaviours are coming from the 5-year-olds, simply gather them while others are outside and talk about being role models for the younger children.  Do not lecture to them but have a conversation about how important they are as the leaders of the class, as the role models in our community.  Simultaneously, have these children give lessons on some materials to others, trying to engage them in more responsible behaviour.

With five-year-olds you can also gather them for a time when we move, laugh, yell, be silly - giving them an outlet for the anti-social behaviour they have mimicked, which they find funny.  If this is occurring in the 5–6-year-olds this might also be a symptom of changing planes of development.