In December's Sandy Hook, Connecticut, school shooting massacre, at least one teacher saved her students by locking her classroom door.
Former school district security chief Vince Matranga says there's a lesson to be learned from that.
"Like what happened in Sandy Hook, that gunman went to the classrooms where the doors were unlocked. The classrooms that were locked, he couldn't get in, went right on to the next classrooms," said Matranga.
That got one lawmaker thinking that it's time to mandate all California public schools have classrooms that can be locked from the inside too.
While newer campuses already have that security measure, as many as 30 percent of schools statewide do not.
"Right now in many of our classrooms, most of the older classrooms, if there's an intruder in the school, the teacher has to walk outside to lock the door because the locks are on the outside of the door," said state Senator Marty Block (D-San Diego).
Block believes it can be done for $30 to $60 per door. But that expense can add up for struggling school districts.
And some wonder what happens if a gunman gets inside a classroom full of kids and locks everyone in?
"The police officers or medical personnel cannot get to the people who may need help inside those rooms," said John Weidinger, a school volunteer in San Francisco.
Senator Block thinks maybe a teacher's key would be needed to lock the door from inside, and that construction bonds could help pay for that.
In Block's own San Diego Unified School District alone, the upgrade would cost $15 million for the new locks, some new doors and labor. Matranga says it's worth it.
"Schools in this country don't have a whole lot right now to defend themselves," said Matranga. "So every little bit helps. And this may not sound like a lot, but actually it is a lot."
Matranga says an electronic system where administrators can lock doors remotely would be better, but that would be financially out of reach for many school districts in this state.