Hi Op. I completely feel for you and know everything you are feeling and going through.
My DD (now 17) missed the whole of year 9 and half of year 10 and 11. She spent the best part of a year in bed anxious and depressed. I hadn't considered Autism until CAMHs suggested she get assessed after a particularly horrific trip to A and e . You are more familiar with it by the sounds of things. She now has a diagnosis of ADHD and Autism which made sense of a lot. It also made me feel less guilt as a parent that I had done something wrong along the way (my ex is awful to me and blamed me for everything)
There are no obvious solutions but the biggest thing that I learnt is that when they can't go to school.. it really is that. They can't. It's not won't .Endless 'helpful relatives and people who think they would do in your situation will come along with suggestions about taking their phone away, giving them consequences if they don't go in, incentivising them to go in, 'forcing' them in etc. It'll pointless as it is either suggesting they are just choosing not to go in and that you are making it too 'nice' at home, or it's punishing them for something they can't actually do.
They need an ally (you) in order to retain your relationship and home needs to be the place where she feels safe. Of course I still encouraged when I thought we might be on a good run but there were points where I just knew it was pointless.
The other thing I realised is that after a few good days at school (Ie if she made it through a whole week or 4 days... it took so much out of her (the school day, the masking and ensuing anxiety) that this would inevitable be followed by a difficult period as she was so exhausted - so I started to expect this after a good run rather than think all the problems were solved.
You work in a school so you know how it works. I always tried to be as proactive as possible in building good relationships with the contacts in the school to show I was as on top of things as I could.
Even with all the trips to a and e, the absences, the diagnoses the school still didn't think if they applied for an EHCP that she would get one. I applied myself and it was awarded after she was assessed.
I know if you work in a school that it must make it incredibly difficult to be at home and with her. I work in an office and thankfully had an understanding manager - plus it really started getting really bad in covid but continued well beyond.
When everyone returned to work, unless she was showing signs of being really depressed I just used to go into work and ask my neighbour to check in on her a few times a day. None of it ideal but she has stopped going to her Dad's and you have to keep your job right?
Sorry I have just completely rambled. It's such an emotional rollercoaster and you just want them to be happy and ok. Nothing can prepare you for it.
But they can equally surprise you in a good way!
My DD missed the last 4 months of school before her GCSEs. I managed to secure home tutoring for 3 hours a day from the LEA and she decided she felt able to back into school 2 days before study leave started. Completely out of the blue. She took and passed 5 GCSEs amazingly and started A levels this year.
I thought we were home and dry as she loved her 3 subjects and seemed to be thriving in the environment.
However she has now dropped out a few weeks ago. All of her friends are off doing university open days and revising for mocks. I am sitting here scratching my head again! She has started a 2 day a week job but I have no idea what the future holds.
I do think she'll be ok in the end ... but (another thing I learnt) .... it may or may not be linear for your DD. It's certainly not for mine but I have had to make my peace with it and trust it will all be ok in the end!
There is an EBSA support thread on here with lots of good advice. You might not be at that stage - and hopefully won't be but it could be useful. I went into this sleepwalking and wish I had known more about EBSA before it happened so I could have dealt with it better at the start.