The way it happened with us is school gave us leaflets about neurodiversity in yr2 but didn't actually speak to us about it. Which left us very confused. And quite angry tbh.
Then in yr3 there were a bunch of issues so we said straight flat out was it possibly ADHD? She had seemed to us as if she'd been actively dropping hints to this point. To which the teacher seemed to visibly blow a sigh of relief. And she started the process rolling.
We are now in yr4. DS has had the first phase of the referral and we'll see where we go. For various reasons I think we'll hit a brick wall tbh.
A friend had someone from CAHMS tell her last year that her daughter was probably ADHD but they wouldn't pick up on it or get a referral for it for years. She's under CAHMS for something else but they can't do ADHD referrals because that's got to go through school. She had been sat with DS at school because the pair of them were struggling with focusing and completing tasks so they'd been given a slightly different activity involving drawing to keep them focused...
Magically with a new school year, I hear from my friend that school are now putting her on the referral pathway... Funny that.
I've had a TA (who works at the school but is a close friend) tell me that they aren't allowed to suggest any type of neurodiversity to parents at all now. They have to wait until parents raise it - unless the child is pretty much in a safeguarding situation which is raising concerns about safety to themselves or other kids. This was pretty much confirmed by other friend (above mentioned teacher in neighbouring county) because the councils don't want to fund referrals.
The thing that pisses me off is the school simultaneously has to observe and refer so the teachers are trained to know what to look for, but they can't tell parents the kid is ticking all the boxes they are taught to look for!
And even if you ask the question, they will only refer if they have 'referral spaces' that year. Otherwise you have to suck it up and wait whilst they tell you there's no issue / issue isn't big enough until it reaches the next September and you enter the next annual referral space lottery.
So the kids who need a referral struggle for long than they should (with consequences to their mental health and education) whilst the rest of the class also get disrupted and the teachers struggle to deal with the whole sorry mess.
Meanwhile if I lived literally 2 miles down the road, I wouldn't have to go through this fiasco, and they'd just assume DS was ADHD and give him reasonable adjustments in school without any of this hoop jumping at all.
It's fucked up.