Compression Vs Quality

I have been asked to help set up multicast video services at the school i work for. these will be distributed hopefully live over the wireless network. therefore size is a major issue. i am used to dealling with completely uncompressed video sources, and so am still learning about codecs compression formats etc. I am jsut wondering what sorts of resoltuoin do you think would be a happy compromise between bandwidth consumption and viewability, what codecs do you people recommend. like i said it is for educational purposes so we don’t want to give these kids eyestrain etc.
thanks