If you do go this route, make sure you document for CYA purposes.
From a security standpoint the best option is setup a captive portal.
Many of the Windows XP machines I maintain at the office don't have this check box enable.
Last week, I did a clean install of Windows XP on a laptop, and when I took it home, I had the validating identity problem and couldn't connect to my home network.
Eduroam is another popular choice for educational organizations.My windows 7 machines connect just fine to the wireless network.