The best solution, assuming you're stuck with CF-based cameras, is to start out the class by showing them pictures of CF slots with bent pins, saying "This cost us $xxx to repair; this year, if you break it, YOU pay for it."

That said, a better option is to avoid CF entirely for students. Hand out cheap cameras with SD card slots. There's a reason that (at least in current-generation cameras) only pro cameras still use CF. CF's mechanical design is terrible, making it highly prone to damage like this unless you treat it with a decent amount of respect. SD, by contrast, is much harder to break, hence the reason consumer gear almost exclusively uses SD, not CF, and has for at least the last decade. Heck, even the newer pro cameras have at least one SD slot these days.

Perhaps let students work their way up to the higher-end cameras after they've proven they can take care of the cheaper ones.

Or just move to newer pro cameras that have SD slots (e.g. Canon's 6D series, 5D Mark IV and later, etc.) and leave the CF slot empty.