Did you perform a factory reset? If so, you may have to use an alternate network like your phone's hotspot to get through the initial setup. You should then be able to connect to your school's Wi-Fi. Some schools have to whitelist your device's MAC address.
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution."
If you appreciate my answer, maybe give me a Kudo.
I am not a Roku employee.