You need to keep stopping them until they learn and understand your expectations. Make sanctions very clear an always followthem. As for hands just don't even entertain them. I always say to my year twos that they need to put their hands down unless it is absolutely urgent and must be heard or answered immediately. If you continue to work while the noise level is too high then they will always think that what they are doing is perfectly acceptable. You are the one incharge and you really need to put all te effort and groundwork in now or you will really struggle to change them later down the line.