Alexa Brennan, a rising senior at Messalonskee High, will compete in the Beach to Beacon High School Mile for the first time. Michael G. Seamans

Alexa Brennan has never run the Beach to Beacon High School Mile. She doesn’t have any teammates who have done it, any friends who have tried it, or any coaches who could give her a pointer or two from having competed before.

So this will be a new experience for the rising Messalonskee High senior. And that might be her favorite part about it.

“I’m going into it a little bit unknowing and I think that’s kind of a good thing,” she said. “I don’t really have a teammate that I can really talk to about it, which kind of makes it exciting, just going in there with so much unknown and so much to look forward to.”

As it enters its fourth year, the High School Mile has become a staple of the weekend as a showcase that runs the day before the signature TD Beach to Beacon 10K. It’s not an easy event to qualify for — male competitors need a mile time of 5:00 or a 5K time of 17:30, and female runners need to beat 6:15 or 20:30 — and Friday, a field of 20 boys and 17 girls that includes 10 individual cross country or track and field champions, will tackle the two-lap run at Fort Williams.

“It’s just a great opportunity to run against the best,” said Griffin Allaire of Wells, who is seeded first after finishing second last year. “There’s not one kid on that course (Friday) that’s not going to have a chance to win.”

For some, like Brennan, the race will be an introduction to an event that’s very much a part of the Beach to Beacon spectacle. There’s music leading up to the event, and a collection of past champions and well-known runners, including Beach to Beacon founder Joan Benoit Samuelson in attendance, and each of the runners has his or her name announced before the race.

“(It’s) definitely serious as far as the competition aspect goes. But (it’s) just a little more lighthearted than that,” Brennan said. “There are going to be a lot of great people there I’m looking forward to meeting.”

Karley Piers of Falmouth, who is seeded third in the girls’ race, also will run the mile for the first time. She’ll then turn around and do the 10K on Saturday.

“It’s a little bit nerve-wracking just because I race against these girls all the time,” said Piers, whose mother, Sheri, runs the Beach to Beacon every year. “I’m more focused on doing well in the mile. I want to get a good time, good place and see how I am compared to some of the other girls. … I’ve heard it’s a pretty hilly course in the fort area, so it will be a pretty good workout for me as well.”

Piers said she’s also looking forward to the ceremony.

“It’s cool how they bring in some of the top runners who will be competing the next day, like some of the elite runners. That’s cool and it kind of makes you feel special. We all look up to those people,” Piers said. “I’m looking forward to seeing everyone there, seeing Joan Benoit. It’s just a fun time of the year.”

For many of the runners, the mile will be a repeat performance. Iris Kitchen of Gorham, Aiden Willey of Bonny Eagle, Jack Bassett of Cape Elizabeth and Allaire will run the race for the third straight summer, and 14 in total will try the mile for the second straight year.

“Honestly, I think I’m just as nervous as I was the first two times,” Allaire said. “This is the last year I’ll be able to do it, I’m a senior. … The atmosphere is great; it’s a really exciting race.”

For Allaire, it will be another chance to take an elusive victory. He was third as a sophomore and second last year, and with defending champion Lisandro Berry-Gaviria out of the field, he knows he has a target.

“I guess there is a certain level of pressure,” he said. “Hopefully the third time is the charm. I’m excited to be first, but there’s definitely more pressure, just from myself, and pressure from family and friends.”

One of the runners looking to catch him is Will Shaughnessy of Brunswick, who’s seeded third behind Bassett and who won the 2-mile title at the Class A indoor championships.