Liberty Elementary School Principal Paul Pack, who was named Washington Post Principal of the Year, arrived at the school six years ago. (Jason Andrew/For The Washington Post)

It’s dismissal time. Fourth-graders wearing paper Krispy Kreme doughnut hats spill into the hallway.

Paul Pack, 41, is wearing one, too. As principal of Liberty Elementary School in South Riding, Va., he regularly helps with dismissal.

“I try to be with the kids as much as possible,” Pack said.

The children are coming from the Decimal Diner, a math activity in which students tackle decimals by pretending to run a restaurant. Pack was as eager to participate as the students were.

“Going to the Decimal Diner is a joy,” he said. “It’s the greatest part of the day.”

Pack is The Washington Post’s Principal of the Year, chosen from 16 finalists from the District, Maryland and Virginia. He’s known throughout Loudoun County as the principal of “the STEM school.”

Pack is wearing a sweatshirt with the school’s logo — a red, white and blue eagle. “2018 FETC STEM Excellence Award Winner” is stitched around the logo’s perimeter. Pack and his team in January presented at the Future of Education Technology Conference and won.

“Anything we’re doing well, we share,” Pack said. “We share so other kids around us, in the state, in the country can get it.”

Since Pack arrived at Liberty six years ago, he has made science, technology, engineering and math the priorities. His school is the only one in Loudoun with a SMART Lab, a technology space equipped with whiteboard desks, a video editing station, a green screen and other technology that encourages students to collaborate.

“I’ve never worked with someone [before] that thrives on putting other people first,” said Nichole Thomas, the SMART Lab’s instructional facilitator.

But the SMART Lab isn’t the only place where students can experiment with the latest technology. Pack encourages teachers to incorporate it into their classrooms, too.

Fifth-grade teacher Emily Nykorchuk recently introduced her students to virtual reality.

“I was so excited, I ran to Paul to share it with him,” she said after she discovered an app that let students create 3-D renditions of the solar system.

“I trust Emily. I learned from her,” Pack said. “Some principals or leaders see [themselves] at the top, and I think they totally have it wrong. The principal works for the teachers and the teachers are serving the students. This building wasn’t built so I would have a job. It’s built so that kids can come to school.”

Before he was a principal, Pack was a teacher. But he didn’t figure out until he was in his 20s that he would spend nearly two decades working in education.

“At the age of 21, actually, I started college,” he said. He went to the State University of New York at Oswego. “It’s a big teacher college, and I just loved it. I loved being with people that wanted to serve others.”

Originally from Long Island, Pack has learned the difference it makes when teachers feel supported. “I mean, some teachers have these off-the-wall ideas, like one teacher wanted to [build] a sound and video studio,” he said. “And my answer is almost always yes.”

Pack helps teachers write grants and come up with creative ways to pay for their ideas.

Liberty Elementary in 2014 hosted its first STEMmerweek summer camp. Families pay to enroll their students in a week-long program that immerses them in STEM-related challenges. In 2017, Liberty launched a coding camp, and the school plans to host its first art camp this summer.

“We generate a lot of money,” Pack said. “Thousands of dollars that we get from the camps during the summer, I pour it back into technology.”

At the beginning of each school year, Pack hosts Laps for Liberty. Families pledge a dollar amount — say, $2 to $5 — for every lap around the school’s track their child can complete.

“The first year we raised $50,000,” Pack said. “We have [more than 1,000] kids, and it’s no stress on the kids. It’s not competitive, and no one gets on your case if you can’t pledge.”

The money goes into a resource fund for teachers so they can purchase what they need for their students — from textbooks to coding materials to instruments for the music department.

And the teachers know they have Pack’s support, not just at Liberty but across the Loudoun school district.

When Katy Greiner, 23, graduated from the teaching program at the University of Virginia, Pack mailed her a gift — a glass apple inscribed with the words: “Katy, most will not remember every lesson, all will remember how you made them feel.”

Pack was her fifth-grade teacher 13 years ago. Now, she teaches at Rock Ridge High School in Ashburn.

“I look at [the glass apple] every day. It’s a visual example of what I should strive for,” Greiner said. “I wouldn’t be where I am today without him.”