Officials in two school districts in Texas believe they have a deterrent for incidents like this week's shooting at Parkland High School in Florida. Selected employees are allowed to carry guns on campus, WFAA reported.

The Argyle Independent School District implemented the rule in 2014, and the Keene Independent School District followed suit the following year.

Teachers packing heat is possible thanks to the passage of the Protection of Texas Children Law that was passed in 2013. The law permits districts to create “school marshals” for campuses, WFAA reported. The marshals must submit to extensive active shooter and firearms training with the state and must undergo a mental health evaluation, WFAA reported. Marshals must renew their licenses every two years.

Signs outside schools in the Argyle and Keene districts warn visitors that staff members are armed, WFAA reported.

Keene Superintendent Ricky Stephens said creating school marshals was needed.

“Administrators and teachers are going to be the first ones who arrive, so do you want them to arrive with a pencil or a pistol?” Stephens told WFAA.

According to the law, weapons must be in a safe -- or on the marshal at all times, WFAA reported.