E.R.
My son is almost 10. He is very bright, but normally extremely polite and well-mannered. In fact, I am always getting compliments from other parents, teachers, etc. on how polite he is. So why does he get this surly 'attitude' with me all of a sudden?!?
I have checked with other moms of kids this age and I think they ALL go through this. The important thing is to just continue to make it clear to your kids that it is NOT acceptable. We made a checklist of things which includes:
1)talking back
2) saying things in a mean voice or with 'bad' attitude
3)doing chores grudgingly and grouchily and not willingly
4)mumbling under your breath, not looking the other person in the face
We've found that it is much easier to be snotty when you aren't looking eye to eye. So we have a rule now that whatever you have to say, you stand up straight and look someone in the eye to say it and you say it clearly.
I emphasize with my son, over and over that HOW you say or do something is just as important as what you say or do- attitude is everything. Also that being kind is more important than being funny or 'smart'.
Sometimes he thinks he is being funny or 'grown up' and I just stop him and say "I know you think that sounded funny, but think about it for a minute. That sounded really rude- how do you think I felt when you said that?"
I tell him that every time you open your mouth, you should pretend your words are being spelled out in front of you, hanging there for everyone to read. Speak as if you can't 'take it back' because you really can't, once it is said. There will always be consequences to speaking without thinking first.
We also talk about after you say something hurtful or ride, even if you didn't mean to, you should apologize to the other person. Just say " I'm sorry that came out so mean. I wasn't trying to hurt your feelings when I said it like that." But that even more important than apologizing is CHANGING THE BEHAVIOR and learning NOT to speak without thinking first.
Kids have poor impulse control, especially at this age when their brains are learning so much other stuff. My son has actually said to me
"I try to remember to think before I talk, but I'm busy thinking about something else and then it comes out and I didn't mean it how it sounded" So I don't think you can be too 'punishment' oriented about it- just keep on repeating the rules everytime it comes up. Writing lines is a way to focus them on it, but we usually go for longer-term stuff.
But if I feel like he is just being MORE surly after I say something to him about it (no one, adults included, likes it when someone points out they are acting like an ungrateful jerk, lol) then we take away play date privileges, Nintendo, family tv shows we watch together, weekend movies, loss of allowance for the week, etc. I don't hesitate to take away that kind of stuff, because we say over and over that those things are a privilege for good behavior, not a right.
This too shall pass- just don't allow the back talk, point it out everytime and be consistent in how you deal with it. I think maturity helps a lot- but then of course they become teenagers!!! At least we'll be well prepared for that! Good luck!