Orchestra director Clayton Allen, center, helps the ensemble warm up before a concert at Lake Braddock Secondary School in Burke, Va., in May. (Allison Shelley/For The Washington Post)

In Afghanistan, Clayton Allen was an Army medic at a field hospital in Bagram, treating soldiers who had been maimed or wounded in combat. To unwind, Allen, a violinist, would play classical music from his tent, the tunes at times competing with the sounds of exploding bombs in the distance to fill the night sky.

Today, Allen is the orchestra conductor for one of Virginia’s largest student music programs at Lake Braddock Secondary School in Fairfax County. There he oversees seven orchestras and 330 musicians from seventh to 12th grade.

On some days, the challenges in this job can seem even tougher than those in his previous one: broken strings, lost instruments, misbehaving students.

“I always tell my parents, ‘This is harder than Afghanistan,’ ” the 37-year-old music teacher said, with a chuckle.

Allen is one of more than 21,000 military veterans since 1993 who have benefited from Troops to Teachers, a Defense Department program to help them get into the teaching profession. The program connects them with training, eases them back into civilian life, provides career coaching and offers them cash bonuses for moving into schools and positions that can be otherwise difficult to fill. Since 2012, it has placed about 800 teachers in Virginia classrooms.

Orchestra director Clayton Allen, center, helps tune the cello of a member of the concert orchestra before a concert. (Allison Shelley/For The Washington Post)

Program coordinators say veterans are an untapped resource to respond to a nationwide teacher shortage that has made it difficult to fill positions at high-needs schools and in math and special education.

“Many of them have the leadership skills and the capabilities to be phenomenal teachers,” said Kim Day, director of Troops to Teachers. “It’s an opportunity to serve again.”

Day said the veterans can help bring racial and gender diversity to the teaching corps.

“It does increase the number of male and minority teachers going into the classroom,” she said.

According to the Virginia Department of Education, 1,080 teaching positions went unfilled across the state this school year, including 316 special-education jobs and 198 elementary positions.

Even in affluent Northern Virginia, schools had difficulty filling jobs. Fairfax County, with the state’s largest school system, had 218 vacancies.

In a state with a major military presence, veterans could help fill many of those roles. The Department of Veterans Affairs counted more than 730,000 veterans living in Virginia in 2015. That’s one of the highest totals in the country.

The program is getting a fresh boost in Virginia, where the state education agency and the College of William & Mary recently received a $400,000 grant to provide know-how and coaching to veterans interested in becoming teachers and to study their needs.

The college also plans to start a mentoring program, matching those who leave the military and wish to become teachers with military veterans already in the classroom.

Veterans in the program have a wide variety of needs. Some must finish college. Others need help obtaining teaching credentials and certifications and help finding a job.

Those eligible to participate include former and retired members of the Army, Air Force, Navy, Marines and Coast Guard, as well as the reserves and National Guard units. Participants, with a few exceptions, can apply within three years of retirement or separation from the military. Those who meet requirements can receive up to $10,000 each in financial assistance.

Andrew Crichton retired in 2004 from active duty with the Marine Corps as a captain overseeing about 200 support Marines at Camp Pendleton near San Diego. He later served as a reservist, and he worked as a construction manager until the housing crisis hit and he lost his job. He said his desire to be a leader again drew him to teaching and an accelerated teacher training program run through the Virginia Community College System in 2012.

Crichton said Troops to Teachers gave him job leads that initially did not pan out, but eventually he was able to find work as a science teacher at West Potomac High in the fall of 2012. The program’s hiring bonus helped ease the financial blow of being on a first-year teacher’s salary, he said.

Today, Crichton teaches physics and chemistry at South County High School in Lorton, Va., and his time in the Marines permeates his tough-but-fair teaching style. He begins every year showing his students a cleaned-up version of the opening scene of “Full Metal Jacket,” in which a tough-talking sergeant schools a group of recruits.

Crichton’s message to the students: “You won’t like me because I’m hard, but I’m also fair.”

He said the Marine Corp taught him how to be an effective leader, skills that carry over from the battlefield to the classroom.

“In the Marine Corps, they teach us a certain leadership style, and those things really work with kids,” Crichton said. “If you expect hard work out of your kids, you got to be organized and put hard work in yourself.”

Novice teachers often have a huge learning curve when they first face a roomful of unruly students. Managing a classroom is not the same thing as delivering orders in the military and getting salutes. Some veterans-turned-teachers report that the program helped make it less scary to start dealing with those kinds of nuances in the classroom.

Allen, the orchestra director, followed a somewhat un­or­tho­dox path. It might be called teacher to troops to teacher.

He taught music in Florida schools for five years before his job was cut. That led him to enter the military. After a tour in Afghanistan, he was based at a military hospital in Virginia. When he left the Army, his Florida teaching credentials were still valid, and he was able to obtain a teaching certificate in Virginia.

Troops to Teachers helped him get reoriented in the civilian world after six years of active duty with the military. He learned how to relax during interviews, and a coach helped him rewrite his résumé. The program also helped him find job openings, such as the one he filled at Lake Braddock Secondary.

Since joining the school in 2014, he has helped grow the music program. Next school year, he will be managing eight orchestras.

Allen said his time in the military made him a better educator.

“It gave me more structure and discipline with my class management,” Allen said. “I’m so much better organized.” On field trips, he said, “it’s like going on a mission because I'm planning every step.”