Lourdes - I'm glad you have had some good results already.
I think you received good advice here. I have noticed that when my oldest has attitude problems, the youngers are soon to follow. Your oldest dd is the "lead horse" (as the Boyers say
), and has a special role in leading her siblings. It helped my oldest to explain this special responsibility to him. He wants to lead his younger brothers in a good direction. Likewise, it helped my middle ds to tell him he is leading our youngest (not sure what I'll tell our youngest).
Also, privileges need to be recognized as such. They are earned. This includes bedtimes, free time, fun time, toys/games/ipods/tv time/movies/music, etc. They can be taken away and sometimes need to be so they are remembered to be privileges. Your Thanksgiving discussion was a good one - I'm glad you saw good results.
I have come to believe that respect in the way dc talk to us is a must. I had my dc saying "I know, I know", just not answering me, or giving great sighs a few weeks ago. My oldest started it, and my middle ds was soon to follow. I finally hung a sticky note up on the cupboard. I told them for every time they did not respond "Yes, mom" in a cheerful voice when I told them to do something, they had 5 minutes earlier of a bedtime. For every time they did not complete all of their chores without being told, they lost their 30 minute computer time for the day. Two days of following through on this worked wonders. They can wear us down sometimes, can't they?!? But, we sometimes forget we have control of their day and that privileges are not a given. I hope you continue to see good results - but be strong, be firm - you are not alone in this struggle, but as homeschool parents, we have more options in our control to change bad habits into good habits. HTH!
In Christ,
Julie
My 12 year old is saying "I don't care" when I point out to her she is behind on her online classes. She spends 5 to 6 hours and only gets 2 lessons done. She has an F in Gifted and Talented Literature, because she did not turn in a project on time, and now her second project is overdue, so she lost her chance to pass this semester. This is not because she cannot finish on time, she was doing better before. It is because she is deciding not to finish on time. My 11 year old is giving me a hard time on grammar. If I tell her to read the lesson to herself, she barely looks at the directions, meaning I have to make her do the written part over when she has done it wrong. This is even though I have her do almost half the lessons orally, and she was doing fine before. Then if I begin to explain, she cuts me off and says in annoyance "I know, I know!" This is wearing me down, any motherly wisdom? I am not responding to these behaviors with great patience 
In the meantime, I prayed this morning. Keri and I had a talk. I let her know I expect her to catch up her work, that if she works extra on the weekend,she can catch up before it gets really out of hand. I told her if she didn't catch up before Thanksgiving, she would forfeit Thanksgiving vacation and have to work while the rest of the family is enjoying the holiday. She did catch up on Literature, which is the class she has an F in. I let her know she now needs to concentrate on Science and Social Studies, which are each one lesson day behind. I praised her for good grades in other subjects. My gut tells me something else is on her mind, because I came upon her crying twice today, but she wouldn't say what was wrong. She can be a moody person at times. I will keep praying.