Right now for you it's getting that EHCP in place. You do not need the school to do this. You can apply directly then you have the right to appeal. Sadly the school do not and the process shuts down for six months if they are refused.
Then you can look at alternatives. We had EOTAS and I had a personal budget plus alternative provision. The LA will hold a list of approved providers. It can take a while to get in but once in it's easy to increase days.
Specialist provision is also a very good option that's often run alongside alternative provision.
Then in year 6, transition from junior to senior, this may be a paper exercise but it's an important time. You can request extra assessments and get the EHCP changed to reflect needs going forwards.
Then working towards adulthood. This starts at about 14. Planning for the big transition from 'senior' school age into adulthood and further education.
This may take the form of supported placements, supported college, therapeutic placements. This can continue until they are 25.
Please know that you can request a social care assessment from the Social workers that work for the LA. A useful document to have to help with identifying need. And getting the needs met through EHCP.
You can also request a carers assessment for you.
It does unfold. You'll need a help to get this right but it's a long process so don't worry about doing all immediately.
I had IPSEA to help me, they are a charitable organisation that help guide you in law.
And I used SENDIASS to help navigate tricky bits with key stages. They are also a free service funded by the LA.
In parallel to the process are the non means tested benefits you need to claim; DLA. You'll need this just to even up the extra expenses of having an autistic child.
Blue badge via the council when you have your DLA
Then when they approach 16, PIP.
Once they are 19, you need to ask for a work capability assessment even if they are at college. This is purely so they can get their NI stamp but it will give access to UC at some point. It's quite expensive otherwise.
And, sorry I know this is long, if you have any other over 18 living with you you can apply once the child themselves reach 18, with the council, to be classed as their carer for council tax purposes . You can't before this time. This gives you the 25% discount. But you'll be getting it anyway if you are the only adult and they are still in education.
I am part of the group 'trauma informed parents' this helps me understand how the trauma caused by autism affects behaviour.
It might be it's as simple as an EHCP and adaptive measures with the current school. But from reading It sounds like the stress response your daughter is showing isn't conducive to learning and she needs a different path now.
You'll get through this. I know it's a hard time. My daughter is an adult now. She says to me 'mummy, I need fierce mummy today to sort things out'. I didn't take no for an answer. They see you are fighting for them although at the time it appears to be a thankless task.
Lots to think about.