Are you asking how to enter the proxy information on your tablet? If so:

1. Disconnect from your school's WiFi network if connected.
2. Open the Application menu.
3. Tap "Settings".
4. In the Settings sub-menu, tap "Control panel".
5. In the Control panel application that opens, double-tap "Connectivity" in the "Connectivity" section.
6. In the "Connectivity" window that opens, tap the "Connections" button.
7. In the "Connections" window that opens, tap the name of your school's WiFi connection to select it.
8. Tap the "Edit" button.
9. In the "Connection setup: Name and type" window that opens, tap the "Next" button.
10. After the window updates to "Connection setup: WLAN", tap the "Next" button again.
11. After the window updates to "Connection setup: Complete", tap the "Advanced" button on the far right.
12. In the "Connection setup: Advanced settings" window that opens, tap the box next to "Use proxy".
13. Enter the proxy information for your school's WiFi connection in the appropriate HTTP proxy, Port number, HTTPS proxy, and Port number fields.
14. Tap the "OK" button to close the "Connection setup: Advanced settings" window.
15. Tap the "Finish" button to close the Connection setup: Complete" window.
16. Tap the "Done" button to close the "Connections" window.
17. Tap the "OK" button to close the "Connectivity" window.
18. Close the Control panel.
19. Connect to your school's WiFi network and test the connection.

EDIT: Bah, I'm too slow.
EDIT2: As suggested by qole below, this information is now in the wiki.