If she's either:
(a) not trained to deal with kids with mental disabilities
(b) a substitute

I'm inclined to think she's a substitute. In which case, the school still should be properly prepared if they're throwing an untrained sub in with a kid who they know has fits of anger.

And if she felt the child was a danger to himself and/or others, it would've been appropriate to call the SRO. Most SROs don't bodyslam non-violent kids to the ground. Most are well-trained and have learned to restrain a potentially violent child in a safe manner.