Is there a way to block access to a specific IP address?

My son attends online school and during school hours I'd like to block access to Discord chat to help him stay focused.

During school hours we use Clean Browsing to whitelist the specific websites he needs for school.  However Clean Browsing uses DNS filtering and I'm not sure if this would apply to a downloaded chat app.

To stop access to Discord during school I believe I need to block access to the IP addresses found on this page, https://www.cloudflare.com/ips/

Is there a way to do this?

Thanks for any help!