How do you protect your kids from school?

My Nicholas has just started school and I am amazed of all that he has learned. However I am just as shocked of the things not so good he has learned. The first two weeks he was talking to me about this game he plays at school called "Kissy, Kissy Girls" I asked him what that game was. He replied thats when all the girls chase the boys and kiss them. They seem to play this game playtime lunchtime everyday. I talked to another mum about this and she didn't seem to be to worried about it. Today I talked to a dad who's daugther has been forced to play the game. He said his daughter is stressed about it all. I suppose its all about being accepted and if you don't seem to follow everyone else then your deemed "different" I agreed with the dad I certainly find this game totally unacceptable and I keep telling Nicholas this however, I'm not sure whether he is being up front with me when he says he doesn't play that game anymore. Furthermore we were having dinner on Tuesday night and I was telling Nicholas he should be eating his dinner to which he replied ïf you say that again I will F... ya!!!"Dave and I were stunned I couldn't believe it. My first thought was do I make an issue of this or do I just assume he doesn't know what he is saying? No i need to make an isssue I would hate him to talk to anyone else like that so Dave put him in time out because he refuse to apologies. After 5 minutes he came back into the kitchen and still refused to apologies. So off to the sink and with the soap dispenser I asked him to stick out his tongue. Tears soon flowed ( I didn't put the soap on) and I just explained that was a really really bad word and he must never say it ever again. I finished with a cuddle and that I loved him. Its hard to imagine it was only two months ago when he was at Montessori playing in the sandpit or swinging on the swings all those innocent games and now 6 weeks into school he has changed. I so wish I had the patients to home school. I have only spoken on those two matters there are other things he does now which he learn't from the play ground. He's only 5years old what will he be learning by the time he's 10 I shudder to think!!!