NATIONWIDE, (AP) – Security companies are succeeding in their quiet campaign to elevate the fortification of schools over other approaches to prevent mass shootings of students.

Industry pushed the “hardening” of U.S. schools for years, but cost and other concerns slowed sales for products such as bullet-resistant doors and smoke cannons that spew haze to confuse a shooter.

An Associated Press investigation shows how the February massacre at Marjory Stoneman Douglas High School in Parkland, Florida, changed that.

Industry representatives saw an opportunity and used an ongoing influence campaign to persuade lawmakers to spend big on upgrades. Since February, Congress has greenlighted $350 million for equipment and other school security. States have approved another $450 million.

Educators and experts say mass school shootings remain uncommon and that mental-health counseling reduces violence more effectively.