So basically, they are, I imagine doing everything that is in the NIL or other assessment documents, but your conclusion is that it is not working?
I would use meeting as a REALLY useful opportunity to gather evidence.
So I would prep a list of all the interventions in the assessment reports/NIL, and start with a nice list of all the things that they are doing with a note of who is doing them and how often. Lots of nicey nicey, thankyou thankyou.
That will give them a warm glow.
Then slip on into the ones that are not getting done and find out where they are with those.
With luck you will be able to come out with a list that they cannot afford and/or are waiting for OT, SALT etc to get back to them.
Then the big question will be - does he need more of anything?
ASD can co-exist with the type of behaviour that responds to behaviour programmes and exclusions, but the classic ASD meltdown is an overload, and no exclusion or star chart will help.
having someone to identify the triggers and to pre-empt overload is usually essential for the sake of dc and the class.
also a quiet room to calm down in.
And then a programme that helps dc to self regulate.
It depends if the triggers are sensory or communication-stress or both. But until the triggers are sorted, my guess would be that the correct answer probably won't be exclusion.
One last thought - if the dc the school are seeing now is really quite a bit different than the dc that the assessors saw when they did the assessment, that is a VERY useful bit of evidence to get into the minutes of this meeting.
Good Luck