My son is in 4th grade as well. We went through exactly the same thing up until the beginning of this year. He is very active in sports, and so we use that as leverage as much as possible. During off seasons, we use the TV, video games, outside play, whatever he enjoys most. If he doesn't give me 1 good hard hour on his homework, then he gets and hour of whatever taken away. If there are any questions after trying to complete it on his own, I will help him, but he has to TRY it on his own first. We also discovered that our son is ADHD, so that with his medicaitons is helping a lot. I think that the back talk and the hard headedness ( LOL ) is an age thing. My son trys to get away with that, but we are very stern with it. Kids need to know that speaking to adults the way they do sometimes is very disrespect full. I make my son appologize, and then may give him an extra chore or take away an hour off of his bedtime. They don't have to be sever punishments, but there should be some concequence for that type of behavior.