I will go and tell them to stop fighting or ask them to tell the cause of fight and try to solve it, and if then also they don't listen to me I would tell the teacher about what happened and she would then take the action
I will stop them and ask the reason of their fight. I will try to solve the problem and make them apologize to each other.I will also tell them that you will lose ur reputation if u fight like that in the playground. If there is a big issue i will call any teacher and tell the problem to him/her.