You need to march your hiney up to that school right now, and have a talk with Mrs. Bxxx, the counselor, and the principal. That is unacceptable for a teacher or school to do. If your kid is being segregated for any reason, as a parent you need to know ahead of time. You also need to be given the opportunity to work with your child to improve these things. Popping them into a special group, and no notice does ZERO to bring the school/teacher/kids/parents together to work as a team, and as far as I am concerned is unacceptable.
Your daughter at 7 shouldnt be having this stuff just dropped on her. If she is below where she needs to be, there needs to be a discussion, and further workup as to why (perhaps dyslexia or some other LD), and tips and tools for Mom and Dad to help. Why didn't they give you something to work with her over the summer if she was below where she needed to be?
Inexcusable in my book. We get one chance to get kids to really become engaged in school, and feel like they get it, are worth it, and help motivate them to continue on that path all the way through, and this is a bad start.
You can quote me if you like, but you and other parents need to speak up now, and speak up loudly.