My daughter has recently received a ASD diagnosis, but prior to this I was fighting for SEN support and stated to the school they couldn't deny this just because there wasn't a formal diagnosis because of long waiting lists.
The result of them not initially listening was my daughter not getting support- such as taking time out when sensory overloads were causing stress and unmanageable emotional outbursts. This led to a few internal suspensions.
Although I understood the school actions, I could also see the detrimental effect on my daughter. I wrote formal emails and spoke to the school and told them to put in my suggested support immediately or they were failing their Duty of Care and I would be escalating it.
Within the week she received the suggested support; small things like having a Pause Pass, knowing the reset room, having one key teacher to turn to. Since that has been in place, her emotional and academic behaviour has been 100% better. No more outbursts. No more time out. In fact, she's now a model for other students.
I have no issue about suspension. However, it needs to be followed up with how to support the child so they know how to function in the real world, whilst getting their needs met.
Be firm about what would work for your child and ensure there is a plan in place.
Good luck xx