There is a documented way to use existing dial plan to do exactly what you wish in the fusionpbx.com member documentation that I don't believe we are allowed to share here. (but it might be posted somewhere already)
There is also the "school bells" optional app that might be of use to you.
Applications for FusionPBX. Contribute to fusionpbx/fusionpbx-apps development by creating an account on GitHub.
github.com