Correction: An previous version of this article quoted Ed Bishop, director of Prince William County public schools’ Office of Transportation Services, as saying bus drivers should have “moral turpitude.” The story has been updated to reflect that he meant strong character.

Operating a school bus is not for the faint of heart. Drivers have to maneuver large ungainly vehicles down narrow neighborhood streets and winding country roads.

Weather — snow and ice, rain, stifling heat — can also rattle a bus driver’s nerves. Traffic in the Washington area, known for being the worst in the country, becomes exponentially more daunting for someone trying to steer a 40-foot vehicle with the turning ratio of a cruise ship. And because no one anywhere wants to get stuck behind a bus going the speed limit and stopping three times in a mile to pick up children, other vehicles constantly pull in front of buses or cut them off.

Then there are the passengers.

Children can be noisy, rude and unpredictable. Every parent knows that driving with just two kids in the back seat can get ugly, fast. But what about having 70 faces in your rear-view mirror? Drivers must not only maintain order inside their buses but also watch for children darting in front of or behind the vehicle when it’s at a bus stop.

Given the long list of challenges, one might expect veteran drivers to be full of horror stories. But most — while conceding that middle-schoolers are occasionally disrespectful and that the weather can be difficult at times — are overwhelmingly positive about their jobs.

“The first year, I did think, ‘What am I doing here? Why am I driving a school bus?’ Because it’s a tough business,” said Patricia Vance, the coordinator for safety and training for Prince William County. “And then afterward, I thought, ‘Wow, I love it.’ I came back every day because I loved it.”

The familiar school-bus-yellow paint debuted at the first School Bus National Minimum Standards Conference in 1939. Buses have gone from the horse-drawn “school cars” of the 1880s to the first steel-body model in 1927 to sleek, contemporary buses with air conditioning, automatic entrance doors and heated mirrors.

The American School Bus Council estimates that 480,000 buses transport more than 25 million students in the United States daily. The buses rarely have serious accidents: Students are 20 times more likely to arrive at school alive when taking the bus than if a parent drives them, according to council data. That is in part because buses are designed for safety, with reinforced sides and high-back seats, and in part because the training is so rigorous.

Vance began driving a bus in 1973. She drove special-needs students until she moved to the office staff in the mid-1990s, she said. When she started, she would go to each of her students’ homes and introduce herself to the parents before the school year started.

“People think about all the challenges, but when I think about it, I think about all the kids, the smiles, the parents trusting you,” Vance said.

Still, there is an industry-wide school bus driver shortage, said Ed Bishop, director of the Prince William public schools’ Office of Transportation Services. Prince William is starting the 2013-14 school year about 45 drivers short of what it needs to run its fleet of more than 800 route buses. Arlington, Fairfax and Loudoun counties also have driver shortages; Montgomery and Prince George’s counties do not have a shortage this year. The D.C. public schools provide bus transportation only for special-needs students, said Keinde Thomas, a spokesman for the Office of the State Superintendent of Education.

“The problem in the industry is not attracting enough applicants, it’s not attracting the right applicants,” Bishop said. Only 20 percent of applicants for school bus driver positions in Prince William make it to the required training. Applicants in Prince William are screened for a criminal background and a safe driving record, and they have to pass four tests administered by the Department of Motor Vehicles to obtain a commercial driver’s license permit.

Once prospective drivers have a permit, Virginia requires them to complete two weeks of classroom training and at least 24 hours of behind-the-wheel training. In Prince William, they average from 40 to 60 hours, Bishop said. The last 12 hours of training must be completed with students on the bus. Bus drivers must also be certified in CPR and first aid. Requirements for obtaining a commercial driver’s license vary by state.

“Most people do not fail at this job because they can’t drive a school bus,” Bishop said. “They fail at this job because they don’t have the other characteristics that are required of a school bus driver: the [character], the driving record, the ability to handle discipline on the buses, the traffic, the hours, the weather.”

Having all of those children in your care is a tremendous responsibility, Prince William School Superintendent Steven L. Walts told the drivers at a training session last week at Brentsville High School.

“Unfortunately, not every one of our kids comes from a house where there’s three meals a day, and everyone’s employed, and everything is good,” Walts told the drivers. “There’s a lot of challenges that many of our students have, and you have that great opportunity to welcome them in the morning and to see them off in the evening. I appreciate not only the safety of your responsibility, but the fact that the way in which you do your job makes a difference.”

Bus drivers in Prince William make from $15 to $30 an hour, depending on their experience. The median annual income for school bus drivers nationally was $27,580 in 2010, according to the Bureau of Labor Statistics.

The job attracts many retirees who like having evenings, weekends, holidays and summers off. It’s also popular among parents of young children, who in Prince William, Loudoun and Fairfax are allowed to bring their kids on the bus with them while they work. Bus drivers in the District and Arlington, Montgomery and Prince George’s counties are not allowed to have their children on the bus.

“It’s a great job for [young parents], because you don’t have to pay for a babysitter,” said Pat Simmermon, a retiree who has driven a bus for nine years. As a former small-business owner, she likes the schedule. Her husband, Harry, has been driving a bus for five years. He drives the bus that two of his grandkids take to and from Mountain View Elementary School.

Albert Luster was in the final stages of his training this month. After retiring from Computer Sciences Corp. in January, Luster did some projects around the house for a few months but became bored. He decided it was time to start working on his bucket list. First up: driving a school bus.

“It was something that I always thought I wanted to do, even back when I was that young tender age of riding on the bus myself,” Luster said.

The biggest adjustments during training, Luster said, have been getting used to the turn ratio and to going no faster than 45 miles per hour, even when the speed limit is 55 (except on interstate highways with a speed limit of more than 55 mph, on which the buses can go 60, according to Virginia state regulations).

On one of Luster’s last training rides, instructor Debby Lear noticed big improvements in his control of the bus.

“On day one it was a lot of ‘to the left, to the left,’ ” said Lear, who drove a bus for about 10 years before becoming a full-time driver trainer. “Now he is in the middle. He has learned to center this large beast.”

Lear said, however, that it’s not maneuvering a large vehicle or corralling rowdy kids that makes the job so difficult. It’s the weather, particularly climbing onto a cold bus first thing in the morning. “When you get on a cold bus, you think you’re going to go on and warm up, but it takes a while,” she said.

Vance also said weather was her biggest challenge. Her worst day on the job was when her bus ran into some power lines that were weighed down with ice. She talked to the students and sang songs with them, she said, to try to keep everyone calm until a rescue squad came.

Bishop said that although it is a difficult job, he thinks that many of the drivers in the county would continue to work if their pay were cut in half, because they say they feel a responsibility to their passengers and their parents. He said drivers who are obviously sick sometimes come to work anyway because they don’t want to let down “their” kids.

“It’s nice to hear that kind of attitude: They’re my kids. I’m responsible for them. I don’t trust them with anybody else,” Bishop said.

Lear agreed. “It’s one of those jobs,” she said, “that it’s very hard to get out of your blood.”