See, this is why I love coaching high school cross country.

Every so often you have one of those days when the kids defy your wildest expectations and suddenly start racing like young Ritzenheims and Flanagans. OK, maybe that’s an exaggeration, but it’s still stunning to see so many of them carve large chunks of time away from their previous bests. I know for a fact that they didn’t just get a minute faster from any special training they’ve done in the last week, so what’s happening?

On Saturday, our school was very busy with Fall Family Weekend and with a traditional Fall Sports competition that takes place every year with our arch-rivals, the Pingree School of Hamilton, Mass. This sort of thing is very common in the private school world, and the way it works is that on one weekend in late October the two schools engage in competition across all the common Fall sports (Soccer, Field Hockey, Golf, Volleyball, and Cross Country). The host site alternates, and this year it was our turn to welcome the athletes and fans from Pingree.

As you might imagine, there’s a lot of school spirit on display. Typically, most of the excitement and attention are lavished on the “ball sports” that are easier to watch, while cross country happens mostly away from the playing fields and out of sight. But this year, someone had the terrific idea of scheduling the cross country races first, resulting in a large contingent of fans milling about on the school’s main Quad where the races started and finished. Since each cross country race counted towards the schools’ final score in the overall competition, there was an unusually high level of interest in the outcome of the races.

So there you have the basic ingredients: parents, classmates, teammates, and even alumni from some of our past teams forming the biggest, loudest, and most supportive crowd our young runners had ever had cheering them on. Still, running is running right? How much difference could a little yelling make?

As the runners started coming in from the boys race, it became clear that it was going to be a good day for fast times. Standing near the finish, I would watch our runners approach, glance at my watch, and do a double-take as I realized that almost every one of our guys was in the process of setting a massive personal best. PRs fell like dominoes, with some boys taking more than a minute off their previous best times boys for 5k.

A few minutes later, the same scene was repeated in the girls race. One senior girl in her fourth year of cross country ran 85 seconds faster than her previous best. Another senior ran 56 seconds faster than her previous best, set in her sophomore year.

As far as the team results, both meets were routs. Although I had not expected either meet to be super close, it was still stunning to see the Concord green and white tide rolling in, sweeping away the Pingree blue. In the boys race, we took 11 of the top 12 places. In the girls race, we took the top six and 12 of the top 16.

But how had this happened? I had been aware that some of the kids were “due” for a breakout race, but to have nearly two-thirds of the team PR was beyond what I had imagined.

About a half hour after the race, I was still pondering this mystery, and I asked one of the girls who had submitted one of the more impressive races on this impressive day how she explained it. “I think we all just decided to PR today,” she said.

Hearing that comment, I remembered how, many years ago, I had interviewed a local runner who had run 2:17 to qualify for the Olympic Trials Marathon. In recounting his early years of running, he recalled his first year of high school cross country, and how he was more than happy to kind of hang out in the middle of the pack with his friends, just trotting along. In the last race of that long-ago season for some long-forgotten reason, he decided to run harder, to step outside his comfort zone for once. he finished near the front and, he said, he suddenly understood the sport in a completely different way.

As a coach, the day when you see it suddenly happen — when you see a kid suddenly get what it means to race — it’s pretty special. And when the whole team decides they might as well all run PRs, well, that’s pure magic.