Lauren Harris knew she’d be walking, she just didn’t know where. The Holtsville walk phenom had a huge decision to make as her high school career entered its twilight late last month — compete in the USATF Junior Nationals in Sacramento, California on June 24 or attend her Sachem East graduation ceremonies on June 23.

And boy, was it a hard decision, with Harris and her family debating it for weeks, she said. They even canceled the trip, only to reschedule it shortly after. But in the end, Harris chose walking, an event that has defined the latter half of her high school athletic career and something she hopes will take her toward international glory in the future.

“I knew that I wanted to,” Harris said of competing in Sacramento. “It was tough on my family . . . it took a lot of convincing.”

It worked out OK. Harris received her diploma at a graduation rehearsal ceremony, went to Sacramento and placed second in the 10-kilometer event in 52 minutes, 47.84 seconds. Taylor Ewert of Beavercreek, Ohio won in 51:12.42. Both qualified for the Pan-American Junior Championships, scheduled for July 21-23 in Lima, Peru, although Harris won’t be going.

“I’m upset that I’m missing it,” Harris said. “But it gave the third-place girl [Nayeli Cisneros of Elgin, Illinois] an opportunity to go.”

Instead Harris will be at Marist College, preparing for the cross country season.

Harris got a taste of international competition in May at the Pan American Games, also in Peru. Her 11th-place finish was the best among American women, according to milsplit.com.

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The junior nationals finish also qualified Harris for the USA vs. Canada Junior Race Walk Match, scheduled for Aug. 20 in Rome, Georgia. She said she plans to compete in that.

“It’s preparing me for the next level and getting me ready for further distances,” Harris said of her introduction to international competition. She said her coach, Olympian Maria Michta-Coffey of Farmingville “travels so much, and this is what it’s all about, international competition and stuff. It’s giving me experience and getting me ready for when I move up in the distances and go to the next level.”

When Harris graduated from Sachem East, she left behind a legacy that will be hard to match, or even come close to. Statistically, she is the fastest high school walker in American history. This season, Harris won the indoor state and national championship, successfully defending her title in both. She also set a new indoor 1,500 meter and one-mile national walk record and outdoor 1,500 walk record.

Harris was part of a Sachem East team that won three consecutive Suffolk outdoor track and field titles and won the Suffolk girls triple crown — cross country, indoor, and outdoor track and field county championships — in her junior year.

“We have such a good culture and, being a part of that, gave me experience of what it’s supposed to be like to be part of a team,” Harris said of her years at Sachem East. “Hopefully, I can carry forward what I learned in high school and use it for college.”