Like most schools we have been looking for a solution for BYOD devices for some time.
We have been using Smoothwall for web filtering for a number of years, together with Ruckus wireless.
Although the combination of transparent proxy and SSL log on page in smoothwall with no wireless security works well, it does have the issue of having to enter log on details every time a device is used, and of course apps don't always display the log on page, or give any indication that authentication