Both propane and natural gas powered school buses are becoming more common today. Here are a few pictures of a BlueBird built propane powered bus (click on the picture for a full resolution version:
Here is a link to a document from the National Association of State Energy Officials that describes propane-powered vehicles in general.
For additional training and information on alternative fuels, check out the National Alternative Fuels Training Consortium, and the National Fire Protection Association. In Pennsylvania, be sure to check out the State Fire Commissioner’s Alternative Energy and Emergency Response programs.
REMEMBER… You have to know what is inside when dealing with ANY vehicle today.