Ok, here is a question I have been longing for a rational answer. This is a touchy subject, so here it goes.

My 2 daughters have a step-mother. She has been in their lives for 5yrs, 3 as a married person. She has called me a whore in front of them (4yrs ago), she has physically hurt them (5yrs ago). All of this I have mentioned to my ex and of course denies all of it. The day after my ex and her got married, they were dropping my girls off to me and my youngest told me that SM said because I do not carry their Dad's last name (I Changed back to madien name) that she (SM) is now their mother. Ok, I talked to the girls and reassured them and they knew who their "real" mother is. It has been a few years, and I notice all kinds of weird things from this woman (SM). First off, Dad is never at school conferences, concerts, etc. It is SM. Her signature is on all of the girls school documentations, from field trip slips, registration materials, records, assignment notebooks, etc. She signs her name under "parent/guardian." Just the other day I was checking my kids MySpace (I monitor them) and I peeked her SM's page and she has a picture on there of my kids, when they were 16mos old and 3yrs. She did not know them then. I can understand the pics of them now when they are older, but when they were babies and I was still married to my ex and we did not know here then? Anyway, anyone know, can a step-parent sign legal school documentation without it going to court? Can she continue to sign things that have an impact on my kids without my knowledge? Morally, I know it is not normal for me, but I was told it is misrepresentation and she can get into a lot of trouble just because she has "parent" in her title, she was never given legal rights or responsibilities (nor will I ever give them to her). Any ideas?

I would think you would have to list her on their school stuff... I know I had to list my husband because he is not my daughters biological father. It seems to me that she is trying to step over the line a bit, maybe in an attempt to make you angry. I would contact your children's school and see what they have to say.
Bottomline, she is simply a step-parent, she has no legal rights over those children and I would be worried what else she is going to try and do while attempting to pass off as their mother.

I agree with macksmom above. Please talk with the school principal about this, but be reasonable and coherent and nice and not blaming so you will not sound like a freaked out, jealous busybody biological mother who thinks she has no control. You are in the right - sound confident and have all your ducks in a row. Good luck!