It is possible to restrict access to Flint to only while on school grounds. We do this by restricting the IP address(es) from which Flint can be accessed. Here's how you can add a specified IP address.
Go to "Workspace settings".
In the left-hand sidebar in Flint, click on "Settings & members" and then "Workspace settings."
Scroll down to "Allowed IP ranges".
Within the workspace settings panel, scroll down to the bottom where you'll see "Allowed IP ranges".
Add IP address(es) and ranges.
Add the IP addresses you want to allow using CIDR notation. You can use a narrow subnet mask to allow a single IP, or you can use a broader subnet to allow a range of IPs. You can add multiple CIDR blocks as necessary.
Remember to click update, and your workspace will now have restricted access to only the IP addresses you've specified!