If Roblox is banned on your school computer, you can unblock it in simple steps:
Login to the account and go to settings.
Look for the Security tab and go to the Account PIN feature.
Disable this feature and go to the Privacy tab.
Scroll down at the screen bottom and have a look at the blocked user list.
Look for your name in the player list and unblock it. Save the changes, and you’re good to go.