Loudoun County Schools Superintendent Edgar B. Hatrick III has announced that he plans to retire next year, ending his more than two-decade tenure at the helm of a district that has grown nearly fivefold and risen to national prominence under his leadership.

The longest-serving superintendent in the region said he wants to spend more time with his family, including three grandchildren. “We have become a lighthouse district in almost every area of our operations,” Hatrick told the School Board on Tuesday night. “This work has been an honor that has defined my professional life.”

His career started at Loudoun County High School immediately after college. At the end of his contract next June, he will leave with 47 years of institutional memory.

He knows everything from “the curriculum to the HVAC [system] to who the janitor at Waterford Elementary School is,” said schools spokesman Wayde Byard. “He can tell you about construction plans and how to do a reading program right.”

Hatrick took over as Loudoun’s superintendent in 1991, and his tenure has been an unusual luxury for the suburban district. The average stint for a superintendent nationally is closer to six years, according to the American Association of School Administrators.

Loudoun Superintendent Edgar B. Hatrick III (Loudoun County Public Schools)

Other Washington area districts will also have transitions at the top. A new schools chief is assuming the top post in Fairfax County in July, and a search is underway for a new leader in Prince George’s County.

For 22 years as superintendent, Hatrick laid the academic framework that many say helped lead to the county’s astonishing residential boom. Under his leadership, the school system grew from 15,000 students in 1991 to a projected enrollment of more than 70,000 next school year. He oversaw the construction of 30 elementary schools, 10 middle schools and nine high schools.

Along the way, Loudoun became a national model for energy-efficient school construction and for many of its instructional programs, including arts and foreign-language offerings, and the use of technology in the classroom.

In recent years, Hatrick has waged pitched battles to secure funding for the growing school system. Spending per student for the coming fiscal year is $11,637, down from $12,780 in 2009.

The pressure to make deep cuts in the school budget has mounted since the November 2011 election, when a slate of Republican candidates swept the county Board of Supervisors.

That same election also saw a majority of fiscally conservative newcomers to the school board. The school board members slashed Hatrick’s proposed fiscal 2013 budget by more than $12 million.

This year, the supervisors expected to make even greater reductions. After after an initial round of cuts, the supervisors adopted a county budget that left the school system facing a shortfall of more than $15 million.

After a second year of charged budget discussions, Chairman Scott K. York (R-At Large) called for a change “at the top” of the school system during the county board’s final budget work sessions in March.

Hatrick said he will help the board select a new superintendent and added that he plans to remain in Loudoun during retirement as a “full participant in the community and educational activities.”

Over the next year and beyond, Hatrick said he plans to continue advocating for more resources to invest in quality programs and technology.

“We can afford what we need to do in Loudoun County,” Hatrick said. “We are not a high-tax county. We are not a high-tax state. Loudoun has the resources.”

Hatrick, 68, graduated from Loudoun County High School in 1963, when the still-rural district had three high schools — one for black students and two for whites. He had plans to go to graduate school and become a professor after the University of Richmond, but he took a job teaching English at his high school alma mater in 1967.

“It didn’t take me six week to realize this is really what I want to do,” Hatrick said.

It was there that he met his future wife and embarked on what would become his life’s work. By the time he turned 30, he was a principal at the school. In 1978, he moved to the central office to become the director of special education, then took over as superintendent in 1991.

Hatrick, who has an annual salary of $249,754, has stood apart from some of his local peers’ spotlight-grabbing style, including former Montgomery schools superintendent Jerry Weast. Hatrick, some veteran employees said, is a personable leader who values the community’s close-knit roots. “As the system has grown, he is still good at keeping it as close to a family as he can,” said Kevin Terry, a guidance counselor at Dominion High School.

Hatrick, a towering presence at 6-foot-5, is known for his steady vision and behind-the-scenes attention to detail.

Employees say his philosophy is characterized by what they call “the shade trick.”

“When he visits schools, he likes to see that all the shades are at the same level,” Byard said. “He knows that if you pay attention to small details . . . it shows that someone cares.”

T. Rees Shapiro contributed to this report.