By Justin A. Rice, Globe Correspondent

When O’Bryant track & field coach Jose Ortega first asked Emily Prado to run the 2-mile three years ago, the long-distance assignment brought her to tears.

“When he told me to run the 2-mile I cried,” the junior recalled during the first day of the Boston City League Track & Field Championships on Monday at White Stadium. “I went into the bathroom, I didn’t tell my teammates, I didn’t tell my coaches, and I started to cry.

“But when I did it, I thought this is something I’m finally good at. I told myself, ‘stick with it, something good might happen.’ I never pictured myself running it for three years.”

Prado not only stuck with it, she has won the event at both the outdoor and indoor city championships for three straight years.

On Monday she did so by setting her personal record, 14 minutes 10.50 seconds — about 40 seconds faster than her previous PR.

O’Bryant, which is going for its 19th straight city title in outdoor girls’ track, was also in first place in the team standings (76 points) after Monday's opening day events. Adrienne Thornton won the girls’ discus for O’Bryant with a toss of 120 feet, 9 inches while her teammate, Kiana Daley, finished second after recording a personal record (112-01).

Thornton, a state champion thrower finished, second in the shot put (33-00.50) behind New Mission/Boston English’s Jamila Jones (33-01). Thornton also finished second behind Latin Academy’s Monique Cox (1:13) in the 400-meter hurdles by .60 seconds.

Her throwing coach, Ted Loska, said she threw well considering she hurt her ankle on a hurdle and the throwing circle was soaked by rain in the middle of the meet.

Latin Academy was second in the girls’ team standings (58.50 points) after Imani Pressley won the 100-meter dash (13.10) and Roxlind James won the high jump (4-06).

The remainder of the running events are slated for Tuesday at 3 p.m.

“It’s slipping away from us,” Ortega said of winning his 20th straight girls’ city championship. “It’s not looking good … This is just the field events. The running events is a whole different system. It’s not going to hold up. The meet is not over. It’s not even half over.”

But while Ortega wasn’t so confident about Tuesday’s running events, he said he’s never seen anyone dominate the girls’ 2-mile in the city like Prado has the last three years.

“I don’t think anyone has won it consistently, back-to-back-to-back,” Ortega said. “That’s an unusual event. No one wants to run it. That’s a long race. It takes someone who is mentally fit to run that race.”

Ortega said it’s one of the hardest events to consistently win.

“You just don’t know,” he said. “Anyone can win it.”

That was evident on Monday when Boston Latin Academy seventh-grader Catherine Van Even finished second in only her third time ever running the event.

“I saw everyone ahead of me was picking up the pace,” she said after clocking a time of 14:13.70. “Everyone was going faster so I decided to pick up the pace.”

Prado wasn’t nearly as good as Van Even when she was in middle school. Prado attended middle school at the Hernandez School so she couldn’t compete in high school track before she got to O’Bryant in the ninth grade.

“In seventh grade I got last place all the time, I was terrible,” Prado said of middle school track, which doesn’t include a race longer than 800-meters.

Prado’s middle school coach, Michael Baugh, however, saw potential in her.

“He said ‘She’s more of a distance runner,’” Ortega said of Baugh, who currently coaches Dorchester High. “He said, ‘the more she runs the better she gets.’ I said I’ll take your word for it.”

Even after she settling into the 2-mile, Prado has had some ups and downs. She said she wasn’t feeling motivated during her last two races going into cities and did not perform well.

“The last two races I didn’t really believe in myself,” she said. “But I had support from my team and my cross country coach and my track coach. It was awesome. It’s like I don’t push myself until the cities. That’s where it all goes down and my adrenaline level kicks in.

“I just told myself I want this."

And now she wants the four-peat.

“I think so,” she said. “I hope so.”

Justin A. Rice covers Boston Public school athletics. He can be reached at jrice.globe@gmail.com. Follow him on Twitter @GlobeJustinRice or @BPSspts.