Disobedient 4 year old who just laughs at punishments

Morning parents, could do with some advice please. My 4 year old little boy started school for the first time early this month. First few days went great, positive feedback, he was enjoying himself. However, in the last 3 full weeks, my wife has been called in by the teacher on 4 separate occasions when she's collecting him from school due to his behaviour, most recently for flooding the bathroom. Following each incident he's been disciplined at home, losing privileges, toys, bedtime stories, etc, but it's got to the point where he doesn't care. Even more than that, he just laughs and thinks being told off is hilarious. School are starting a behaviour chart and we're doing the same at home, but we've run out of things to try. He's already confined to his room, where there are no toys or anything, when he misbehaves, but he just sees it as a game. Corporal discipline is something I was subjected to as a child which I will not repeat, but I'm ashamed to admit that this morning I came close to smacking his bottom.​We just don't know what else to do. Has anyone else been through this and can offer any shining lights? via /r/Parenting https://ift.tt/2nbUbEN