Need work-related Legal Advice

Hi! I've been injured (C5-6) for 4 years now. Two years ago I decided to try going back to work. I was an elementary teacher previously and chose to return to the same building as an "instructional coach" even though the building is not handicapped accessible because I wanted to return to my colleagues/support system. Modifications were eventually made to a few restrooms but nothing more. After the first year, I was requested to work this year on the second floor. Since I can stand and walk short distances with assistance, I agreed to climb the stairs (23 of them!) each day with help and work on the second floor where I kept an additional wheelchair. Now that the school year is almost over, administration is "suggesting" (insisting) that I transfer to a different building in the district which is accessible. They feel that the building is hampering my ability to perform my job (Well, duh!!!) and that I am a liability due to risk of injury on the stairs, etc. They also say that next year I would need to work on multiple floors and that no one will be available to assist me in going up and down the stairs...as if I would actually want to do it more than once a day. Unfortunately, they seem to only be offering me one choice of alternate position and it involves switching from elementary to middle school, something with which I have no experience and little desire to do.
I want to know who to talk to in order to find out my legal rights in regard to my situation. I feel like I'm being shoved around with very little control over my future work environment. The school district does not have to update my current building because they have other buildings which are accessible and to which I can be transferred. Any advice would be appreciated.