Especially boys are little different and casual .I am a mother of twins (a boy and a girl) and I see the difference in nature itself. Don't shout and thrash him. Just tell him subtly once or twice and leave it. Nagging doesn't help, it only brings out the negative changes that we don't want to see. With my son I don't nag and start doing things with my girl and within minutes he comes and does what I want him to do. Don't thrash him it will only create distance between both of you.