"This means nothing! My DD is diagnosed Autistic but shows zero traces of it at school! Here, her behaviour has me in tears, thinking I can't do this any longer etc etc. Yet at school she's absolutely perfect. Apparently it's masking (in girls particularly). They spend all day masking their behaviour at school and then let loose when at home.
I'm not saying she is Autistic, obviously not as I've never met her! I just mean don't disregard the possibility due to her behaviour at school being great"
This. 100%, this.
@Bestofthebestt, your daughter sounds exactly like my son at that age. My son is ND, would have the most horrendous meltdowns at home (never in school - his behaviour there was exemplary all the way through to leaving at 16), but at home, after school, if something wasn't how he thought it ought to be - he'd kick off. He had (still has, at 17) a very black and white, no grey areas, view of the world/his life and if his routine changed even in the slightest way... my God, did I know about it! Luckily, his Reception teacher has a ND son herself, and she recognised traits/little quirks of behaviour, and pushed for an assessment. Turned out that he was masking at school, mentally exhausting himself because he was trying to fit in with the other kids, and then coming back to where he felt safest - and dropping the mask. But he is a boy, and as others have said, it's easier to pick up autism in them, than it is in girls... which might be why her teachers are faffing about and essentially rewarding her for her bad behaviour the night before (I get that they mean well, but... WTF?!).
With my son, we find that when he gets to that point of breakdown, a bath or shower helps. When he was younger, sometimes we'd have to physically put him in a bath, but by the time he was around 8-ish, he'd take himself off when he recognised the "tells" himself. Weirdly, his meltdowns lessoned after a traumatic brain injury when he was 6, but I definitely don't suggest that as an answer at all!
When my son was born, so less than 20 years ago, the notion of girls being autistic (mildly) was something everyone scoffed at. I know 4 girls the same age as my son (a litle older and a little younger) who have been diagnosed with it in the last few years. One of his godmother's claims to have a diagnosis made last year, and actually... my behaviour was "good at school, horrendous at home" too when I was growing up - and I know I mask a lot (because I'm introverted, mainly).
I'd speak to your GP, if I were you, and ask for an assessment to be done. But I'd also stop the rewarding of behaviour at home, by the school, because at home - that's for you and her Dad to reward, not a teacher who has who knows how many other kids dancing through her brain!