I think that you should focus more on the positive behavior that the children are exhibiting. If they continue misbehaving, start taking away favorite toys. There must be consequences for their misbehavior. When the students do something well, reward them with a sticker. Make a REALLY big deal about good behavior. You can even have a sticker chart that lists all the children's names. In a given week, when children have received 5 stickers, at the end of the week, they could receive a special reward...movie, certificate, ice cream party, etc. The children who have not received the 5 stickers would not participate in the special activity.
You are going to have to focus less on the negative and concentrate on the positive. I am sure that the children do something great some of the time. Make others an example when they manifest the correct behavior. The other children will begin to get the message.
When the children do misbehave, just tell them what they should be doing ---and move on. If they are physically hurting one another, remove them from the situation and or remove the object that was causing the problem.
When they are not listening, it is time for them to refocus. Do not yell and scream. Have all of the children stop what they are doing and discuss the situations. They may need to put their heads down on the tables for a few minutes and then listen to a story. When things are getting out of control, you MUST gain the control back. If you are yelling and screaming and getting upset, then that is the model that they are going to follow.