Chernet Sisay has a far different reason. The Brookline High senior runs because he is happy to be alive, and he’s going to do anything it takes to make a name for himself.

Sisay is approaching his sixth year in this country after spending the first 12 years of his life in Ethiopia, the last three either on the street or in a crowded orphanage. His parents died of AIDS when he was 9, though he never even knew they were stricken with the deadly disease. Understandably, it was a shock.

Now, he is the top runner on the best high school boys’ cross-country team in the state. Hefty expectations, sure, but nothing compared with the expectations he has for himself.

“What motivates me? The fact that I’m actually out there running,’’ said the 17-year-old.

“I have to take advantage of it. I’m just going out there doing what I’m doing. Running isn’t the easiest sport. It’s not made for everybody. So the fact that I have this gift - I don’t want to waste it. I really don’t.’’

Sisay is 5 feet 8, no more than 130 pounds dripping wet. Life is good, a far cry from a few years ago, when a stress fracture in his back derailed his chances of making the high school’s soccer team.

He had a hundred reasons to be depressed, but not being able to play a sport that he had practiced on the streets of Ethiopia - using a sock stuffed with garbage as makeshift ball - was the freshest of his frustrations.

At the urging of his adoptive father, Sisay switched gears and went out for the cross-country team as a sophomore.

On Wednesday afternoon, after finishing a tri-meet at Larz Anderson Park in Brookline, Sisay was in a chirpy mood. He chatted freely about his past. He stumbled over a word here and there, nothing unexpected from someone who had to learn English on the fly.

His parents’ deaths certainly were not easy for him to talk about, nor his separation from his sister, Bethlehem, nor his old friends who became child soldiers and whose whereabouts are unknown. But he’s someone who understands emotional pain, having gone through more than his share, so he remained stoic.

Sisay is a runner now, and he won’t let anything get in his way.

“I try to tap into that at times and try to tell him to use it for motivation,’’ Glennon said. “At times, he’s very protected about it. I try to push him to tell other kids more about it, like, ‘I was on the streets when I was 11, stop whining and start doing something.’ ’’

Glennon has a story to illustrate just how far Sisay has come since fleeing Ethiopia. One time over the summer, he said, Sisay’s adoptive parents, Vin and Hope Connelly, “went away and left him here. So they gave him money. And instead of using it for the food he was supposed to buy, he went and bought shoes with it. He loves shoes, has a closet full of them.

“So he’s an American teenager now. Some of that past, and who he is, it’s still there, but he’s been here for almost six years now and he’s very much become just like everybody else.’’

“I think the running has saved me as a person,’’ Sisay said. “The way I see things now is completely different because of my running. I’m disciplined in an entirely different way now.’’

His form still needs work. He leans back a bit too much and his elbows aren’t quite at the angle they should be, but his body is still growing. Glennon thinks he’ll make an even better college athlete, since the races are longer and “his endurance and cardiovascular are his best skills.’’

But Sisay has been through enough to know not to look too far ahead. He helped propel the Warriors to the all-state title last November at Gardner Municipal Golf Course with his 10th-place finish, the top Brookline finisher. But Glennon has set the bar even higher this season, eyeing a trip to the regional, and then national competitions.

In the tri-meet against Bay State Conference foes Dedham and Weymouth, the first eight runners to cross the finish line were wearing Brookline red. Second-year Weymouth coach John Connolly didn’t bother running his top eight, saving their legs and conceding defeat before the race even began.

Connolly explained: “You go into it as a coach and you think, ‘What are our chances of even pulling an upset?’ And that would be the upset of a century. We figure we’ll pick our battles.

“Nobody likes the Red Sox outside of Boston, because they’re good,’’ added Connolly. “If you’re outside the place, you don’t like them. You love to hate them. Right now,’’ he said, he’d put Brookline “as the gold standard in Massachusetts.’’

The Brown Invitational meet scheduled for yesterday would serve as another measuring stick.

All 60 of Glennon’s runners have a way of challenging themselves, from Sisay and classmate Mark Perry right down to the newcomers.

“I remember the first day when I was here,’’ said freshman Ethan Goroff. “We do quotes of the day, and the quote of the day was ‘Brookline cross-country has not lost a dual meet in six years.’ It gave us a little bit of a perspective. It was a little bit intimidating.’’

For Sisay, running has become a ticket to an education unthinkable in his native country. His language skills may hinder his ability to go straight to a Division 1 collegiate program - though he has been offered full scholarships, and University of Massachusetts Amherst coach Ken O’Brien stopped by to watch the meet Wednesday - but Sisay is willing to do whatever it takes to be successful.

“I wake up every morning and I’m . . . lucky to be alive,’’ he said. “So I feel so lucky to be a part of this team, in a good environment.

“There are colleges offering me scholarships, phone calls that make me feel good about myself. If you get an offer, let’s say from University of Connecticut, hey, that’s a pretty good school. But if I work really hard, I might get a phone call from Harvard. You have to work really, really hard. Running has taught me that.’’

Jason Mastrodonato can be reached at jasonmastrodonato@yahoo.com.