This is not normal behaviour , u have to take it seriously . But u should not shout or threaten the boys . As they are very small children if u shout them they may get scared and try hiding out things from u . Better is to counsel them together and then individual . Shouting them will have a negative impact. First explain them that this is not the right behaviour and they educate them calmly . Let them know the need to change their behavior and praise them if they agree to listen to u . This type of treatment is called as positive reinforcement as it encourages them to do right things and listen to u .