Personally, I wouldn't go in with guns blazing, but I wouldn't have her do it either. I am in the exact same situation (except at a public school). Ds goes to 5th grade for math, and like you, 5th grade math starts on Monday. If ds had come home with a 3rd grade sheet, I would have politely sent an email to the teacher and said, "just to let you know, dd mistakenly was given a 3rd grade sheet." I can't imagine having her do it. I mean, I have an *actual* 5th grader, and if he came home with 3rd grade math, would I have him do it? If your child came home with the kindergarten spelling list, would you have her do it?
To me, the situation is no different. Last year, my ds sometimes had homework on days when other second graders didn't, and sometimes he had no homework when other second graders did. In the same way, ds10's 5th grade math and literacy are tracked and homework is different for each group.
To be honest, it does seem like you're over-reacting and it worries me that your dd was so upset because she thought *you* would be upset. I'm not thrilled with the scheduling we've had to do to accommodate ds8 going to 5th grade math, but I'll be darned if I'll let him know. I've convinced him that it's the best thing ever. Gifted kids have enough stress without them worrying about US being stressed.
I'm NOT dismissing your frustration or your concerns- believe me, I have BTDT (ds8 is my youngest of four gifted kids and dd19 is entering her senior year of college). It is enough to make you scream at times dealing with the school system, and that's without the added frustration you have of paying tuition.
One thing I would try if you haven't done it already is to write everything done. Actually, this might be a great opportunity to do it in a natural way. You can send a note saying, "I just wanted to clarify things because dd came home with the wrong homework. It was, I'm sure, just a mistake, but I did want to make sure we're all on the same page." And then, write things down.
For example, I had to add things like, "ds will do rocket math in the same sequence as the higher grades," and "when the homeroom class does math extended response writing activities, the teacher will provide 5th grade level work." I wanted to make sure that he was given the opportunity to be just as successful as the older kids.
Don't be confrontational - you can even blame your dd if you have to - "dd seems to be getting mixed up on the homework. She brought third grade math homework home today. Can you help her make sure she picks up the right page every day?"
Obviously, if this doesn't work...
THEN go in with guns blazing. smile But the schoolyear is still new and you don't want to alienate her teacher yet.
Good luck!
Theresa