Anonymous wrote:You need to supervise much more
This.
Think of parental attention as the ultimate positive reinforcement. I am sure that you have heard this before, but kids prefer positive attention, but they will take negative attention over nothing (especially if there is a lot of affect with it). So, whenever your kids are doing something right, give them tons of positive attention. Whenever they are misbehaving, more or less ignore them.
-Your daughter is playing nicely in her room...sit on the floor with her for 5 minutes and ask her about her game. Play with her.
-When she comes outside after fighting with her brother, tell her to stay outside and away from him, but keep it low affect and don't get too involved.
-If she starts helping with the yardwork, give her lots of praise.
Right now, you are kind of doing the opposite. I get it. We have all been there. Kids seem like they are playing nicely, so you sneak off to get something done. Then they start fighting, so all of your attention turns to them. As soon as they calm down, you go back to what you were doing and ignore them. They want your attention, and they know how to get it.