I am coming from the child's side, because my mom yelled at me a lot for the littles things. and let me tell you- yelling at him will not solve anything. People shut down when they are yelled at. Do you really think he's listening to you through all that? That he will suddenly have a change of heart? Or do you want him to be scared into doing it? Simply tell him the consequences of not doing it (ie. you can't sit at the table and eat dinner if you don't wash up) and let them deal with the responsibility.