Should teachers and staff at schools be armed? John Stossel and producer Maxim Lott made a video analyzing that question, and used CPRC research to do so.
More information on concealed handguns at schools is available here. There are a couple of nitpicking points to make about the video. The accidental discharge in California occurred at a firearms training class outside of normal school hours. It was not a typical school environment. One fact the video doesn’t mention is that 18 states currently have teachers and staff who can carry permitted concealed handguns, though the rules vary considerably across the states.
Here are two graphs from the video based on CPRC research (raw data is available here).