More than half of all states have some type of law allowing teachers and other school employees to carry guns on campus.

[Paladin]

What states allow teachers to carry guns at school? Tennessee and Iowa weigh joining them

Just over half of all states allow people with concealed carry permits to keep loaded, unlocked guns in their cars on campus.

Looks like Iowa's proposed requirements are pretty significant:

Those who want to carry firearms at school under the bill would have to go through a permit process that includes one-time, in-person legal training covering qualified immunity, emergency medical training and communication training, as well as quarterly firearm training and annual "live scenario" training.

USA Today uncritically mentioned this:

A 2023 report from the Giffords Law Center to Prevent Gun Violence documented about 100 incidents of guns being mishandled, left in reach of children or accidentally discharged at schools over the last five years.

Looking through the incidents.... many of them are LEO related. Some are simply unauthorized people bringing a firearm in a school. One was a parent who is a convicted felon leaving a gun in his car. That one points to how absurd the laws are... criminals aren't obeying the laws anyway. So the USA Today article is factually incorrect.