There was a lower end ATI card sold to schools in B&W G3's (my first B&W came with one, forget the model now), retail was the Rage 128 with or without the DVD decoder I think.

Just looked here:

http://www.lowendmac.com/ppc/blue-white-power-mac-g3.html

They mention a Rage Pro for some school models with video capture (sounds like what I had).