The aggression is the fight or flight coming out in him because essentially anxiety is designed to keep you safe. Talking to you will sideline it for a while, it won't make help it in the long run.
And what happens when you can't take that call? Feeding the baby, driving, etc? Because one day it will happen, and his anxiety will explode.
Put together a sensory box for him. Photos of you, and his favourite things, a note from you reinforcing you will be there at x time to pick him up, a blowing activity (it calms the breathing, my dd loves bubbles). Something to squash, something to manipulate, something to look at.
Send him to nursery with an item to "look after" for you until you pick him up.
Let him take a teddy, make it smell of you. Give it hugs that he can "use" when he needs one.
Give nursery a step by step action plan. They aren't always going to be able to see him start melting down, so they need to know what to do when he does.
They will need to encourage him to use his space, and use his tools as he won't always know when the anxiety is going to hit. Tell them his shows...what does he do as his first signals that anxiety is rising? My dd pulls at her clothing and scratches her neck.
Talk to him about how anxiety works, and why. Anxiety is normal. We all have it, it keeps us safe. But with him, and my dd, it works over time and sees non threatening situations as threatening. I tell my daughter that we need to help her brain calm down (that's what the sensory box is for) and train it to start recognizing true threats, not perceived ones (she is 10, so maybe easier for her to understand)
Pick him up 5 minutes earlier, or later than the others. Ask the staff to allow him to sit in his quiet space until the noise/scuffle has passed.
Be careful with LED lights, they can flicker and hum. This causes my asd friend to disassociate (not dangerous, but she stares blankly, doesn't communicate and can't function) so be aware of that. You don't want to add to this.
The problem with this is it isn’t tackling the core problem, in fact it is feeding it I agree, especially with letting your friend listen to you with a stethoscope, it is only feeding his anxiety.
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