Hi danhughes and welcome!
Have you tried entering your user name, then tapping in the password field and entering there without hitting the return button? If you can't see the password line there is usually a hide-keyboard button that will lower the keyboard until you tap in a text field again.
If that doesn't help there were some posts a while back about school WiFi systems being different and how to get into them. I could probably find the old threads if you think you need them.