I'd say what the teachers aid did was smart, personally if I had been in that situation I would have gotten up and done to the teacher what she did to the kid, which wouldn't have been so smart.
I'll admit as much as this view may be disliked; looking after disabled kids is difficult, I worked as a teachers aid teaching disabled kids and it was very challenging (worse I saw was the teacher generally babying the disabled kids who were more than capable of tasks given to them), my ex-step-sister is also autistic and pretty destructive with it, which gets you in a really bad mood at times. BUT you never ever hit or shout at a kid like that, any child, least of all a disabled child, less so again with autistic kids who may be particularly traumatised by something like that - never an excuse.
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Bloodheart
Good-looking girls break hearts, and goodhearted girls mend them.