So sorry to hear of this. Some may wonder whether the individual, knowing the principal and teacher support your son, may have planned for the moment when both of these supporters were not present in order to take their unpleasant actions against your son, believing they would be undetected.
I don't have any way of finding out the full story.
You may wish to document what you do know, in a dated journal at home, in brief points. For example (using a fictitious scenario):
1. Son on playground, standing near monkey bars.
2. Female adult, name unknown, blue hair, paisley jacket, nametag on lanyard, standing near hopscotch.
3. Female adult, name unknown, magenta shoulder-length hair, blue pants, red handbag, walked up to female with blue hair and began discussion.
4. Female with blue hair pointed at son.
5. Received phone call from blocked number, 7:17 p.m. informing me XYZ occurred.
6. Son's description and anonymous caller's description match.
All information in this example is manufactured.
While some may agree on requesting an investigation, you may also wish to protect the anonymous caller who reached out to you.
Therefore you may wish to NOT report the existence of an anonymous caller when requesting an investigation. Just have it documented at home.
