Do you have the correct pass phrase and SSID for the school connection? Otherwise your connection might be rejected.
On the Upper Right Panel, Left clicking on the connection icon, shows you available wireless connection the system has found. Click on the correct SSID and when prompted type the CORRECT password.
When using a cat5 cable make sure Auto eth0 is active, click on it to turn it off, click again to turn on.
Right clicking on the connection icon, Gives you to the option to enable wireless, and enable networking. Enable Networking is for the cat5 cable. If I'm using cat5, I usually right click on the connection icon and disable wireless.
Right clicking the connection icon, you can see connection information. This will tell you what ip address you machine has been given by the server. The MAC address of your eth0 card, the connection speed, etc.
If you want your machine to automatically connect to the hotspot (making sure you have all the required and correct information from the school) Right click on the connection icon, click Edit Connections, Add Wireless and put all the info into the correct sections.
I usually connect to hidden wireless connections. I just left click the connection icon, and choose Connect to Hidden Wireless Connection, on the connection input box there is a drop down, click on the drop down (inverted triangle) to see networks you normally connect to. I just choose one of the many pre-configured connections, and click the connect button.
Also check that the wireless is physically turned on the laptop/netbook, usually a keyboard combination key FN plus a function key, or a slider button on the side or front of the laptop/netbook.
Let me know if you need more help. When asking for help give more details on your machine, manufacture and model of notebook etc.