(Getty Images)

Almond, N.Y. mom Laura Brace has no trouble remembering the day in 2009 when she found her children's school bus driver behind the wheel, smelling of booze.

"I asked her, 'You're really not acting normal. Are you okay?' And she's like, 'I'm fine.' And I said, 'Could you breathe on me?' And she said no.

"So I followed her on the bus and I said, 'You know, I really want you to breathe on me.' I demanded that she did, and she finally did, and I could smell alcohol on her breath," Brace told "20/20."

But school officials didn't have to take Brace's word for it. Footage from a surveillance camera on the bus showed students, worried about the driver's handling of the bus, begging her to pull over. When she finally did, that was when Brace, who was waiting for her two young sons, confronted her.

That day, the surveillance camera did little more than chronicle a near-tragedy. But some say that the increasing use of surveillance cameras on buses can actually improve safety, largely by acting as a deterrent to misbehavior among children.

"The number of times children are written up [for misbehaving] is reduced greatly when students know there's a videotape of their every activity," said Dr Alan Ross, the president of the National Coalition for School Bus Safety. "We know their behavior improves. When their behavior improves, there's less distraction to the driver."

There doesn't appear to be hard data to show a reduction in accidents correlated to camera use - with just one percent of all student-transportation fatalities occurring on school buses, they're already considered to be the safest mode of transportation to and from school - but other experts say that, at least anecdotally, they've noticed the safety benefits that come with surveillance cameras.

Cameras can help enforce the simple but important rule that students stay in their seats while the bus is moving, said Bob Riley, the executive director of the National Association of State Directors of Pupil Transportation Services.

"The bus is an extremely safe vehicle as long as the student is seated properly in the seating compartment…They (know they'll) get caught if they walk up and down the aisle," he said.

Riley estimates that as many as half of the new school buses on the road today come equipped with cameras. Some school districts that can't afford cameras for every bus still install casings for cameras so students never know whether or not they're really being watched.

And even though cameras have been known, as in the case in Almond, N.Y., to document driver misdeeds, experts say the cameras are largely a benefit to drivers - particularly in the case of disputes between drivers and students or drivers and parents.

"We have found, for the most part, [the cameras] have protected our members because sometimes reports by parents and the children are not correct and that verifies the worker's position," said Michael Cordiello, the president of Local 1181 of the Amalgamated Transit Union, which represents 14,000 school bus employees in New York City and its suburbs.

Meanwhile, Martha Thompson, the Almond, N.Y. driver caught driving drunk on camera, is hoping that her experience will serve as a lesson to others.

"She is asking everybody to learn from what happened to her," said her lawyer, Thomas Trbovich. "She had no intention to ever hurt anybody, and for a very responsible person, she did a very irresponsible act."

ABC News' Michael Mendelsohn contributed to this report.

Watch more shocking school stories in "20/20: Classroom Confidential" online here.