Dear Ms. Dadia,
If this situation was an anomaly - i.e., if your son has no pattern of acting with such aggression - I'd handle it by (a) underscoring that physical aggression is absolutely not permitted as a way of expressing
angerIslets of langerhans
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Pancreatic islet cell tumor, (b) giving your son some consequence (e.g., half hour time out), and (c) requiring that he apologize to the victim either
faceFace pain-to-face or in writing.
It sounds like the situation was mismanaged, and that deserves some attention (both by empathizing with your son and perhaps by addressing it with the teacher), but it shouldn't be construed as a rationale for your son having acted in an unreasonable fashion.
I don't see any need for the intervention of a clinician.