Since the cameras were the school's cameras, the suggestion that you use the Canon software that came with the cameras won't fly. The school owns that software not you.
You fail to say what version of Photoshop you are using so specific answers to what you should do are not possible. In general, when your PS doesn't handle some new flavor of RAW, do the following:
1. Update the Camera RAW plugin (ACR) for your version of PS to the newest available for your version.
2. If the newest version of ACR your PS handles still doesn't handle the files you need to either:
a. Download and install the newest version of Adobe's DNG Converter.
b. Upgrade your PS to the newest version, updating or replacing your computer if necessary.
Since issues with these Canon files are likely to be a one time or limit occurance, I would suggest option #2a if #1 fails. As long as you PS is at least PS/CS (or PS Elements v4, I believe) and you've upgraded its ACR to at least v2.2, using the DNG Converter is an excellent sollution.
The DNG Converter is a free download. Its Adobe's way of "updating" old versions of PS to handle newer RAW files. Its an external app that converts camera specific RAW flavors into the "universal" DNG RAW flavor. The converted files are still RAW files and will still open in PS throught the ACR plugin. Its an additional step, but the price is right and, if you aren't doing it too many times, reasonably painless. The DNG Converter is a batch converter so it can do a whole folder of files in one operation.