9yr old sons behaviour.

[Teawithatwix]

I have a 9 yo ds. He is intelligent, well behaved at school, can be kind if he chooses. However I fell that all the time I am asking him to be nice to dd (5) all day long he winds her up and it makes me cross. He seems to relish be unkind to her. He can also be lovely to her but the middle ground doesn't happen very often. He is argumentative, he lies, he speaks so rudely to me and dh. At school there are no problems, the only trouble we have is when he is asked to do his maths homework at home we can have a complete meltdown sobbing shouting throwing things. It all sounds pathetic now but I just cannot cope it is constant. If one of us has him on his own he is fine. Dd is so well behaved it drives me mad when dh tells me we (me) are doing something wrong. I don't know what to do I just want to cry.

[FannyFifer]

I have no advice but you are pretty much describing my 10 year old DS and all the rest of his class.
So kinda normal behaviour, ur not doing anything wrong, i put it down to hormones & onset of puberty.

[twoandahalftimesthree]

What are the consequences when he winds your dd up? I have had great success in moderating my 9 yo ds' behaviour by allowing him only a certain amount of screen time (1.5 hrs) a day and then use the 1,2,3 magic method of counting inappropriate behaviours. When he gets a 3, he loses a certain amount of time off the 1.5 hours, usually about 10-15 mins, depending on the behaviour. You can use the same method for both dc, just choose whatever consequence motivates the individual. For dd its time playing out with her friends.
If you absolutely stick to this with no backing down it will certainly motivate a change in behaviour- just be aware that there might be an initial testing time when behaviour gets worse as they try to see if you will stick with it no matter what.
Don't start it without absolutely committing to it tho as failure to stick with it will undermine your authority. I would def recommend reading the 123 magic book as it helps you implement it very effectively.