Sgt. Mayra Franco is always on the lookout for anything out of the ordinary when patrolling a school campus.

"Things that are out of place, people that shouldn't be there. That's our main priority," says Franco with the Stockton Unified School District Police.

A supervisor, Franco has worked over 10 years for the district.

She is one of 35 officers who patrol school grounds, elementary to high school.

"I believe that schools in our district are very safe today. We've taken many measures over the past several years to ensure the safety," says Stockton Unified School District Police Chief Anne Brewer, who has also worked for the U.S. Justice Department, CHP and as an officer with the governor's police detail.

There are 55 schools in Stockton Unified, each is a closed campus and surrounded by a fence.

Classrooms are also locked and so are school lobbies. A visitor must sign and check in at the front desk.

A security system with cameras are in place at every school.

"And we constantly are revaluating what our policies are, what are procedures are, and going through hypothetical scenarios or situations on what might happen and how we might respond," says Brewer.

And think they aren't watching once the school is out? Guess again.

Stockton Unified has 24/7 surveillance of every school from its dispatch center downtown.

And they train for the worst.

“We have an emergency services coordinator that works for the district and part of his responsibility is conduct drills though out the year,” says Brewer.

And in Lincoln Unified, Lincoln High School starting this week is requiring visitors to show their driver’s license and have it scanned as they enter the campus.

“And that’s uploaded into a data base which is secure and it’s myself and one of our assistant principals are the only ones that have access to that," says Lincoln High School principal Terry Asplund.

For now, the only guns allowed on Stockton Unified campuses belong to uniformed officers.

No staff members are allowed to carry concealed weapons.