(CNN) In the year since a troubled teen gunned down 17 people at Marjory Stoneman Douglas High School, shootings have continued at schools across America.

Since Parkland, by CNN's count, there have been at least 31 incidents at K-12 schools in the United States in which someone was shot. That averages out to a shooting every 11.8 days.

In those shootings 19 people were killed and another 44 were injured.

"School shooting has become a cultural thing in the United States," says Mike Clumpner, president of Threat Suppression, a security consulting company that specializes in active-shooter response.

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