Is insurance a problem for schools that allow staff and teachers to have guns to protect against mass shootings?

From the Arkansas Times:

An item yesterday about the Clarksville School District's plan to have more than 20 teaches and staff members carry concealed weapons next school year as a security measure prompted a lot of discussion yesterday, including on the topic of insurance. 

In Kansas, a major insurance company has said it will not insure schools that allow district employees to carry weapons. It prefers that people with guns be uniformed, qualified law enforcement officers. Clarksville has provided security guard training and additional weapons training for its staff members, but they will be carrying concealed weapons and they will continue normal duties, not work solely on security. 

I asked Superintendent David Hopkins about insurance and he sent this repsonse by e-mail:

"I have spoke with them and as of now there is not an issue. I don't expect one either."

Other schools have allowed teachers to carry guns (such as the Harrold Independent School District in Texas that has had it since 2008) and presumably since they have continued to operate, insurance has presumably not been a problem.