"We’ve been writing school business for almost 40 years, and one of the underwriting guidelines we follow for schools is that any on-site armed security should be provided by uniformed, qualified law enforcement officers,” Mick Lovell, EMC’s vice president for business development, told the Des Moines Register. “Our guidelines have not recently changed.”Note that the decision is based on their longstanding policy, not on statistics from the experience. Considering how small the number of school districts that allow staff of any kind to carry is, and how small the number of school shootings is, that's not surprising. I went to the source to see if they had statistics, but they don't. EMC says it's not a political decision, but a financial one. Without actuarial data, it's a guess. They believe it raises the risk they're subject to, but have no idea how to price that risk, so they're refusing to insure schools that might produce that data.
The problem here is that in our litigious society, the availability of insurance could end up setting the policy. School liability insurance has already had effects on the activities available to students; seen many trampolines in schools lately? And I can't say that without remembering the Simpsons episode where they put a trampoline in the back yard, and the final scene with the back yard covered everywhere with injured kids.