I'd contact the LEA and ask for one of their assessors to come to the school. At work we have trained assessors and they assess as part of the display screen assessment, if you self assess that equipment doesn't "fit" for whatever reason. They then suggest adjustments, or equipment gets changed if it can't be adjusted.
There are all sorts of criteria. For example if you are above a certain weight, then standard height adjustable chairs cannot be used. If you are taller than (I think) 6'4", the desk has to be adjusted.
I was assessed because of backache when sitting at work. Turned out to be connected with the length of my thigh bone and not being properly supported.
When I returned to work after my broken leg an assessment was offered, but because the chair I had supported the full length of my thighs and I could make other adjustments with the chair, I was able to sit comfortably.