Snotty 9yo

Maybe something is going on with him. Have you sat him down and ask if there is anything going on in his life, at school?
If he is talking back, take away his favorite items starting a day at a time, then next time he talks back make it a week and so on and so on.
What kids dont complain or whine.

talk to the school, ask if he is being teased or bullied. See how is behavior is there.

You know, mine started getting mouthy when he was prepubescent. He's still a mouthy 11 year old. Yesterday I implemented a new rule around here. Your smart mouth must mean I'm stupid. Since that's the case, I'm too stupid to do various cleaning chores around the house. Since you're so smart, you must be the skilled worker I need and YOU get to be in charge. His chore yesterday was cleaning the kitchen floor on his hands and knees, something I had been meaning to do anyway.

This morning I told him so are you going to mouth off yet? Because I have a huge list of chores that's just waiting on your smarts. He told me heck no... He worked too hard on that floor to want to do something else.

If you do this, make it something above and beyond one of his normal chores. Those have no pull IMO.

I take DD13's allowance away in three week increments. Mouthiness has a high price in this house. She lost over a hundred bucks for one tantrum. The next time she was warned her attitude would cost her she settled down right away.

My 11 yr old does it, too. I chalk it up to puberty and punish as I always have. Take away privileges, extra chores, grounding. Once I told him, "If you're so smart, then here: you balance the checkbook, pay these bills, go grocery shopping, and oh, while you're at it, get a job!" He looked at me and said, "I don't know how to do any of that!" And I said "Exactly. But I do, which is why you shouldn't talk to me like I'm some kind of idiot. You may know some things I don't, but I know way more than you, and until you're much older, that's not going to change." It fixed his attitude for a couple of weeks. lol

9 year old complaining and talking back? It sounds like he's entering tween-dom. This is a normal stage of development - not to say you ignore it. By all means address it and let him know it's not acceptable behavior; however, understanding where the behavior comes from goes a long way in dealing with it.

Kids this age are starting to pull back and look to assert their indepenence. They are going to push back. They are going to roll their eyes and complain. Frankly, I'd be concerned if my 10 year old wasn't occasionally hitting up the attitude. When he's getting mouthy we are firm in response. Loss of privledges if appropriate. A simple "Excuse me. You did not just speak to me that way, did you?" I also work (not always successfully) at watching how I talk to him and how I handle frustration. Kids are going to learn to deal with stress and disappointment by watching others. (cont)

I also think it's important to realize a kid's frustration or disappointment is normal. If I'm telling my son to get off the computer when he's in the middle of a game, he has a right to be disappointed. He does not have the right to ignore me or to be rude. But he does have the right to be disappointed. If he expresses that with a sigh and a "Really? No fair!" That's fine. So be it. I will say "Yeah, really." If he starts to really push it, then there are consquences. If he cooperates (even if he does so while grumping a bit) there's not.

I try to avoid sarcasm. You know, we get mad when our kids flip us the attitude but we don't stop to think about when we're throwing it around. It's an example we're setting. I don't respond to whining. I ignore it and tell my kids I just can't hear/understand that tone. :)

Puberty.