Sorry that this happened to your son. I don't have any experience in dealing with this, but have read some good resources online.
http://www.stompoutbullying.org/index.php/information-and-resources/parents-page/what-do-if-your-child-being-bullied-and-resources/
Interestingly it says on the top...
IUSD is currently building Eastwood elementary (opening August 2017), and there are 2 more elementary schools in the works.
Heritage Fields K-8
The newest K-8 school, located within the future Heritage Fields development, is scheduled to open in August of 2018. The school will serve future...
Gentle Giant based out of Somerville,https://www.gentlegiant.com/.
They have an office in SF, not sure if they service SoCal.
Good luck with your move.