"According to the analysis, 4.1 million students had to participate in at least one school lockdown during the school year, and on average 16 campuses per day across the U.S. were placed on lockdown. There was not a single day between Labor Day of 2017 and Memorial Day 2018 without a lockdown, according to The Post.

Of those lockdowns, 15 percent were reportedly due to bomb threats, while 61 percent were related to firearms."

thehill.com/policy/national-security/422937-more-than-4-million-students-participated-in-lockdowns-over-2017-18