If Kelsey Koons looks too young to be teaching a third-grade class, it’s because she is.

But that hasn’t deterred the 18-year-old from today’s lesson at Loudoun County’s Hillside Elementary School, which has Koons teaching students to identify nickels, dimes and quarters.

“It’s smaller in size than a nickel, but it’s worth more” she says, waiting for students to chime in with the correct answer. When they do, Ms. Koons smiles.

Once she leaves Hillside for the day, Ms. Koons, teacher, will become Kelsey, high school senior. That unusual transformation is at the heart of an experimental Loudoun program to recruit and train the next generation of local teachers before they graduate from high school.

“It’s like the farm team for the majors,” said Shirley Bazdar, director of career and technical education in Loudoun. “We want to give them the chance to ignite that passion and eventually bring that fire back here.”

In one of the country’s fastest-growing counties, where several hundred new teaching positions open up each year, the demand for quality instructors is hard to meet, officials say. Even harder is recruiting high-achieving Loudoun natives, who often leave the area or select another profession before attempting to teach in their back yard.

Tired of losing talent, Loudoun introduced Teacher Cadets, one of the region’s first programs aimed at growing its corps of educators. Eight years later, the program is seeing the fruits of its labor: Members of the first generation of graduates have started jobs as full-time Loudoun instructors.

Six years ago, Betsy Anfind­sen was where Koons is — trying cautiously to navigate life as an elementary school teacher and a high school student.

“Getting that classroom experience at such a young age really gives you an idea of what the profession is all about, what it means to be a teacher day to day,” she said.

Now, at 23, she stands confidently in the center of her classroom, instructing the newest class of aspiring teachers. Anfindsen’s voice booms with authority.

She comes from a family of educators, and she has always enjoyed spending time with children. But it wasn’t until her student-teaching stint that the idea of a career in the field really appealed to her.

That knowledge also helped her in college, where she studied education. And it gave her an unexpected professional boost: Contacts in the Loudoun school district who were eager to hire her upon graduation. “I left with an understanding of how the system in Loudoun County works,” Anfindsen said.

Across the country, rural school districts — often with limited resources, high poverty rates and lagging academic achievement — have taken to handpicking promising teaching candidates. These districts have found that homegrown instructors, who know their schools and regions well, can help turn around troubled schools when attracting outside teachers is logistically and financially difficult.

Those initiatives have been embraced by the Obama administration, which has introduced scholarships and other incentives to bring talent to rural and crowded classrooms. Virginia’s Department of Education has applied Loudoun’s model across the state, attracting teacher candidates through a program called Teachers for Tomorrow.

Loudoun is generally considered a high-achieving district, and it is one of the wealthiest jurisdictions in the country. But school officials say they still struggle to attract talent. It hasn’t helped that budget cuts have left Loudoun with one of the lowest average teacher salaries in the region.

The Teacher Cadet program has grown from 34 students in 2002 to about 200 this year across all 12 county high schools. About 20 of the program’s graduates, like Anfind­sen, have returned to the district to teach after graduating from college, and Bazdar expects to see many more soon.

“We know the caliber of students we produce here,” Bazdar said. “They’re exactly the kind of people we want to bring here as teachers.”