Children of divorce

My boyfriend has a nine year old and a three year old boy. The are really great kids. I am the first woman they have seen their father with besides their monther. The have 50/50 custody so they are with us a lot. We ususally get along great. Yesterday, when we picked the little one up from pre-school, the teacher said that he had raised his hand to srtike her, was being defiant and lying about things. We have noticed a light increase in this behavior along with the development of a bad temper. Is is me? Do you think he is having a hard time dealing with the chance? Is he just a "bad"kid or maybe just his age?

[waitingwithhope]

It is probably all of the above--it is his age, he is probably having a hard time dealing with change and he is starting to get to the point where he realizes that his actions can change those around him. They are quite bright at this age :) If you have only been in the picture for a short while, then he is also dealing with the change and trying to bond with you but stay loyal to his mom. He also may be doing this to seek out attention...maybe for whatever reason he feels like he needs more attention.
I would not worry much if it was a one-time event. If he tries to hit, calmly say "no, hitting hurts" and gently restrain his hands and then redirect his attention onto something else (they can be easily distracted). If it continues happening over and over again, then I would be worried.