Not Provide An Accomodation

I have stage IV cancer and receive chemotherapy treatments. I'm also a school teacher. I have made several accomodation requests to my employer to move me out of such a high stress position but I either got no response or was told that the school district doesn't offer accomodations to classroom teachers if they have a disability that would require they can't teach at full capacity.

My first request was to be transfered to a school that didn't have such a high stress environment with as many high needs children. I received no responce.

My second request was to teach physics which is made up of 11th and 12th grade students only since they are more mature and much less stressful to deal with. I was specifically told, I could "not teach physics students because I had cancer it wasn't fair to the juniors that I be out for chemothereapy when they are tested by the state their junior year." (Is that discrimination? It's not my fault I have to take off every Friday for chemothereapy. Chemo isn't offered on weekends or I'd be doing it then.) So obviously my schedule this year includes 3 classes of wild, wild freshmen biology students.

My third request was to be considered for a job opening which I did qualify for at my own campus that would allow me to leave the classroom environment and focus on helping teachers. I would have decreased my stress load, allowed me to not be in contact with so many students, and to not be on my feet all day. I was told that my interview was perfect and that I obviously was qualified but that they wanted someone with more experience.

This ones just plain discrimination... I think!
I applied to be a representative for our school for a program that pays you extra money if you attend 10 professional developments during the school year. I did it last year and applied to do it this year but was told that I couldn't participate because I have to be out so much for chemotherapy treatments already. Can they deny me professional development opportunities based on days I haven't even taken off yet, because I have to take off for chemotherapy?

And finally, my doctor in an attempt to lessen my burden at work wrote a restriction that asked the school district to change my job functions to ones that require less physical activity and are less stress inducing. (aka get me out of the classroom where students cuss at me all day, set fire to my table-tops and are just really hard to control.) I was told that the school district doesn't give accomodations to classroom teachers that lessen their ability to be in the classroom 100% of the time and full capacity and that until my doctor lifted the restriction I can't come to work and would be forced to take sick leave? Can they do this to me? I've taken lots of initiative to get myself out of the classroom environment and accomodate my students and the school? Are my requests unreasonable and can they actually deny me accomodations?