Make sure Adobe Flash Player is enabled. All the games work, but some may take up to 30 to 40 seconds to load because of large size. Have Patience!
Vex 3 has been released in HTML 5 as well as Flash version, and this page contains the unblocked flash version to play at school and home. If you want to get your hands on older versions, then try Vex 2 and Vex.