Students who returned to school in Fairfax County on Tuesday were protected by added security measures placed by the administration in recent months.

After the shootings at Virginia Tech and Newtown, Conn., school officials nationwide reviewed safety protocols to help prevent mass tragedies. In Fairfax, all high schools this fall are equipped with state-of-the art door-access technology that allows administrators inside the building to monitor who comes in.

Enhanced safety practices also ensure that teachers and staff know what to do in case of an emergency. A bomb threat Tuesday called in at Westfield High School turned out to be a false alarm. But administrators immediately locked down the school and called police, who responded with two K-9 teams to sweep the premises.

Fairfax schools security coordinator Jim McLain, a retired police officer, said he relies on his 21 years of experience in law enforcement to help students remain safe.

“To some extent, we are that ‘in case of emergency break glass’ group,” McLain said. “We’re heavily relied on to be there.”

After the Newtown shootings in 2012, McLain helped lead an overhaul of the door-access systems in the county’s elementary and high schools. At the time of the shootings, five elementary schools and all but one of the county’s 22 high schools lacked advanced door-locking systems. Now, McLain said, all front entrances at high schools in Fairfax are equipped with new door-access systems.

McLain said he helped lead an initiative to expand video surveillance systems at schools across the county. The county’s 1,300 cameras can be accessed in real time by administrators on site and remotely at other locations.

“I think closed-circuit television has become as fundamental to today’s society as doors and window locks,” he said. “We want their kids to be safe in schools.”

Mark Bomber, marketing director at Tyco Integrated Security, said the company provides the door-access and video surveillance systems used at schools across the county.

The county has such a close relationship with Tyco, Bomber said, that the company employs one representative who works exclusively with Fairfax to address the school system’s security needs. Bomber said the representative attends high-level meetings with schools officials to keep up on the latest security issues.

“We’re integrated into what their future plans are,” Bomber said. “We want to understand what the plans are for the school district in the future, so we recommend solutions that are not nearsighted so they don’t have to tear it out in a year to put in a new one.”