Johnathon Carrington, 21, walks the halls at the McDonough School of Business at Georgetown University, from which he graduated in May. (Allison Shelley/For The Washington Post)

When Johnathon Carrington graduated as valedictorian of Dunbar High School, he barely paused to take in his success. Even as he wrote his commencement speech, he worried about whether the D.C. public school system had prepared him for what would come at Georgetown University — a few miles and a world away from his subsidized apartment complex and the open-air drug market that thrived outside.

“I don’t think I’m going to fail everything,” Carrington said in 2013. “But I think I’m going to be a bit behind.”

Over the next four years, he would experience serious academic challenges for the first time. He would struggle to find his place on a campus where students were mostly white and far wealthier. He would even consider transferring to someplace a little more comfortable, where he felt he belonged.

But he would persist. And — unlike so many others from neighborhoods like his — he would make it.

Carrington, now 21, graduated in the spring from Georgetown’s business school with a double major in management and finance. After struggling with math classes and time management in his freshman year, he had abandoned his plans to study finance. But by his junior year, he had reversed that decision, realizing he could rise to the challenge.

“Given where I come from, giving up wasn’t an option,” he said. “I wasn’t going to stop.”

Just 9 percent of the nation’s poorest young people — those whose family income puts them in the bottom quartile — earn a four-year degree by age 24, compared with 77 percent of those in the top quartile, according to census data. It is a divide that both defines and reinforces American inequality.

The odds are better for disadvantaged students who enroll in a four-year college — but even making it to that point is no guarantee of success. Fewer than half of those in the bottom income quartile graduate within six years, according to federal data.

For students coming from stripped-down schools where teachers tend to focus on reaching basic proficiency on multiple-choice math and reading tests, the leap to college academics can be overwhelming. Unforeseen fees and the cost of books and supplies can drive a student into financial peril, while taking a job to pay the bills can get in the way of studying.

For Carrington, who had a significant scholarship at Georgetown, the most difficult thing about college was navigating a new and unfamiliar culture, where he felt always on the outside. “There’s not a lot of people I can relate to,” he said in 2014 at the end of a freshman year that resembled an endurance test. “I can see it, the way people look at me.”

Carrington, then 17, laughs with family on his high school graduation day in June 2013. (Jahi Chikwendiu/The Washington Post)

Now 21, Carrington is looking for a job to launch his career in finance and sports management. (Allison Shelley/For The Washington Post)

It felt like a constant drumming of you-do-not-belong, the difference between the Sperry Top-Siders so common on campus and the Nike Air Jordans on his feet. He was often the only black man in his classes. Once, he said, a white female classmate touched his hair and asked him if he planned to cut it. He had let his curls grow out.

“She called it fuzz,” Carrington recalled. “I was in shock.”

It was not just his race that set him apart on a campus where more than half of 7,500 undergraduates are white and 6 percent are African American, according to federal data. It was also his class and his neighborhood. The median family income of Georgetown students is $229,000, according to a study by the Equality of Opportunity Project.

When Carrington considers what helped him make it through college, his first answer is his refusal to fail.

His second answer is David Peake, a classmate who grew up in a neighborhood like his in Chicago, and who understood what it felt like to be an ambitious young black man at an elite college. They became close friends.

“You never really get used to feeling like the ‘other,’ ” said Peake, who also graduated in May. “It’s more so you mature. You get comfortable with being uncomfortable. But it’s pretty much an everyday struggle.”

Carrington walks past a tour group of prospective students on the steps of Healy Hall at Georgetown University. (Allison Shelley/For The Washington Post)

They leaned on each other. When one of Peake’s best friends was killed back home during sophomore year, he shared his mourning with Carrington. When Carrington felt like giving up on Georgetown, he turned to Peake for a pep talk.

Carrington had a web of other supporters, too. Rashid Darden, a 38-year-old Georgetown alumnus who also graduated from a local public high school, was his mentor. His business-school adviser, Deborah Coburn, met with him biweekly. And in the background were people such as George Seff, an Arlington father of two, who met Carrington occasionally for a meal and helped him out with money for books.

The two met after Seff read about Carrington in The Washington Post four years ago, and sent him a check in care of Dunbar High.

“It wasn’t the first time I had done that. But Johnathon was the first and only kid who responded with a thank-you note,” Seff said. “He’s a solid kid, he’s got a good head on his shoulders. . . . I’m totally rooting for him.”

Carrington grew up moving between homes with his mother in D.C. and his father in Kentucky and West Virginia. Neither of his parents has a bachelor’s degree. But they set the expectation early that he would graduate from college, that he would not be derailed.

When Carrington walked across the stage to receive his Georgetown diploma on May 20, they were there, beaming.

“I pushed him because I saw greatness. I said, ‘You can’t be mediocre,’ ” said his father, John Ackles, 53, who is retired from the Army. “It’s a blessing to just watch him, as his father. I’m happy.”

Carrington works on a cover letter for a job application as his mother, Valerie Carrington, watches. (Allison Shelley/For The Washington Post)

“Now another chapter is beginning in his life,” said his mother, Valerie Carrington, 62, a child-care provider. “I want him to get established. I want him to go to church. And I don’t want him to hang out in the streets.”

Carrington seems more relieved than jubilant. And once again, he doesn’t seem to let himself indulge in enjoying his accomplishment.

Instead, he is focused on landing a job, the first step on a career ladder that he envisions will end up in sports management, with two master’s degrees along the way.

Carrington hopes to start in private wealth management — a job that would give him enough money to live comfortably and help his mom, but wouldn’t require Wall Street’s breakneck workweeks. Though he has been warned that it can take six months for new graduates to find a job, he is hoping to move more quickly.

Like many other recent grads, he is living at home for now and itching for independence.

“I love my mom to death, but I want to have my own place, my own things going on,” he said.

As challenging as Georgetown was, he said that he is grateful to the school for the way it forced him to grow. And he thinks he will appreciate it even more as time passes.

“My grades weren’t the best, but it prepared me for the world,” he said. “The last four years, it was a lot to grasp. I wasn’t perfect at it, but you know, I finished. I finished on time. I was a double major. It’s not like I took an easy route.”

Carrington greets a friend in the neighborhood near the apartment where he grew up and now lives with his mother. (Allison Shelley/For The Washington Post)