https://kidshelpphone.ca/search?keys=Cyberbullying
This is part of the Kids Help Line, which is a Canadian resource. It is targeted to kids but is a good resource for parents to share with their children. It provides access to counseling
https://www.commonsensemedia.org/cyberbullying
Commonsense media is American, and is general resource for understanding kids within a technological context. They provide a lot of good information and background for parents
about cyberbullying.