Some articles to help you and your kids safely discuss bullying and preventing bullying at school and online.
https://azpbs.org/bullying-prevention/
https://youtu.be/C9Ce1Cgcfq8 ("Stop Bullying: Speak Up" a 23 minute video made by The Cartoon Network)
https://www.unicef.org/end-violence/how-to-stop-cyberbullying