Naturally you have a note of where the chariot race sequence in your departmental video of Ben Hur starts, and you get it out when you reach the topic of the Circus Maximus. Here is something additional, from the Discovery Channel website:
There used to be bits of video, which are no longer available as far as I can tell, but there is a chariot race game, where you have to avoid bits of debris on the track while driving at full speed. I'm useless at quick-reaction games like that, but I guess most teens would do well at this one. You can find it also at Channel 4
Also on the site are pages of information about chariot racing, and a click-on-bits-of-the-picture-for-information picture of the Circus Maximus.
Good if you have a data projector or even an interactive white-board, or a class small enough to get round a computer.
For ancient pictures (mosaics etc) of racing from Trier and elsewhere, and photos of reconstruction models, try the vroma site.