hi, a similar situation happened to my nephew. at the beginning of the school year of of his teacher was strong and rude to him because he was not walking fast, he was a few minutes late in class. my nephew requested the teacher to speak to his counselor about the reason of him being late to class.. the teacher got even rude at him, that day as soon as I saw his face I knew something had happened at school. when he told me I contacted the school/his counselor and told her what just happened.. she apologize to me, to his mother and to him.. the teacher almost get spell from the school..
My nephew is a cancer free kid (10months now) with a Rephysis implant in his right leg (a prosthesis inside his leg) reason why he walks slower that kids his age. after that incident the teacher try to be funny again, until we went to the school and confronted him.,.since that day, thanks god everything has getting better, he is popular at school and his classmate love him...Justice, fight for Justice..Kids deserve Respect!!sometime adult do not give the proper respect to kid...

I was going to suggest that you look at your parents handbook or whatever website outlines the disciplinary guidelines in your district, and see if your daughter's punishment was appropriate. It does sound harsh, and based on what you've shared, it seems to be above and beyond what the guidelines would have indicated.

It seems like you need to document what has happened in writing, as unemotionally as you can, sticking just to the facts as you know them. I would handcarry the letter to the school district superintendent's office tomorrow morning, and say something along the lines of "Dear (Superintendent), On (date) my daughter (name), a 7th grade student at (name of school) was involved in an incident during a passing period in the hallway. She was accused of not walking fast enough to class, and being defiant to a security guard, although several students who witnessed the event said that she was singled out for disciplinary action. While I was not there to see what happened, (later that day) I spoke with (Mr. Name, Assistant Principal) and he indicated that the usual punishment would be (ISR). Contrary to the (guidelines in the parent handbook) my daughter was given (a 2-day out-of-school suspension in addition to serving ISR next week.) I respectfully appeal the suspension she was given as it exceeds the district's own guidelines. Students can not learn if they aren't in school. My daughter is an honor student who regrets being involved in the incident, and I feel she has already learned her lesson. I would appreciate hearing from you today. I can be reached at (number.)
When you drop off the letter, you should get the name and signature of the person you give it to, should you need proof of delivery later on...

My child is 13. This is not the first time my child has been reprimanded. It is her second time this school year. She was put in ISR earlier this year for horseplaying. I feel she learned her lesson. She is a good kid and an honor student also athletic and very into school. Yes, it is a public school. When I spoke to assistant principal,he told me ISR was the normal punishment for what they said she did. We had a slight disagreement and he decided to suspend her 2 days and give her ISR next week when she returns. Totally inconsistent of guidelines.

How old is your child? Was this the first time your child has been reprimanded for any kind of "violation?" Is it a public school?
I'd like to recommend that you repost your question in the Educational Laws and Violations Group at community.greatschools.net/groups/77570