We started the diagnostic process for DD when she'd just turned 7, and finally got the diagnosis by the time she was 9.5.
It was her struggles with socialising with other children, some sensory issues (around clothing and lighting/noise) and with any disruption to her routine that clued us in, but in hindsight there were earlier signs that we just didn't recognise.
She was an incredibly high needs baby - barely slept, even from the day she was born (she's still a dreadful sleeper), and cried all the time if she wasn't being held by me. As a toddler she had dreadful "tantrums" that I now recognise were meltdowns, and was very tough to toilet train - was 6 before she was reliably dry.
Before she started school she had some good buddies, but the older she gets the harder she finds it to relate to other kids. She's 10 now and pretty lonely and isolated. Seeing her with other kids, I think she's better liked than she realises, but she can't recognise overtures of friendship - she's got such a fixed idea of what it means to have friends, she doesn't recognise she's actually got some.
She's super bright and very academic, so the school aren't worried, and all the diagnosis seems to have done is give them some box to tick to say they're supporting her. They've not been great, tbh. My goal for secondary school is to find one that sees the whole child and is as interested in her mental health and well-being as they are in her academic achievements.
She's an amazing, clever, loving young woman with a great sense of humour and an incredible imagination, but she's vulnerable in ways I hadn't fully appreciated when she was younger, and I worry about her future and how to support her.