In their blue caps and gowns, Sia Kanu and Zac Winland blended in with the rows of graduating Lee High School students Monday. But unlike the hundreds of other seniors in their Fairfax County class, the two 19-year-olds represented a tiny sliver of the county’s student population: Both are homeless and living apart from their families, fending for themselves while trying to overcome harrowing pasts.

“I’ve been waiting a long time for this,” Kanu said. “Because of everything that happened, I didn’t think I’d make it.”

As other newly minted graduates in Fairfax County and throughout the region focus on the beginning of adulthood and a path to living independently, Kanu and Winland already know all about living on their own. They are a part of an increase in student homelessness in Fairfax County, which had an estimated 2,445 homeless students so far this year, school officials said.

Kanu and Winland belong to an even smaller group, about 355 students in Fairfax who are defined as “homeless unaccompanied youth,” those living without a fixed address and without parents. They battle far more than most just to get to school every day, let alone to graduate.

For a time, Winland lived in the back seat of a Honda Civic. Going hungry for stretches, he lost 20 pounds. Kanu, a former war refugee from Sierra Leone, worked nights and weekends mopping floors at McDonald’s to earn enough to buy her own food.

For both students, homelessness was a secret they shared with only their closest friends. While some teenagers dread going to school in the mornings, Lee High became a refuge for Kanu and Winland. There, they felt free from the stresses of their hidden lives; pop quizzes and research papers didn’t compare to scrounging up money for meals.

Thousands of students in the Washington region share their struggle. In Montgomery County, officials said 906 homeless students attended public schools this year, including 20 unaccompanied youths. About 2,480 students in Prince George’s County were homeless, including 60 who were youths living alone without their parents. In Loudoun County, about 948 students this year were homeless and about 317 of the total were considered unaccompanied youth. Officials said about 2,300 homeless students attended D.C. public schools this year.

The stories of how Kanu and Winland ended up on their own are rooted in tragedy.

Kanu was born in Sierra Leone’s capital, Freetown. She remembers the oppressive heat, her family’s broken-down shanty, the talk of war.

When she was 8, her family fled to Northern Virginia. Just two years later, her mother surrendered custody of Kanu to one of Kanu’s older siblings. Kanu said she faced years of abuse there, enduring physical beatings with an electrical cord that left scars.

“I would find excuses to stay out of the house,” Kanu said. “I would go to my teachers after school and ask for help on homework even though I didn’t really need it. I’d go to the mall and walk around. Home was hell.”

At times, Kanu acted out in class. Ernette Martin, an assistant principal at Lee, met Kanu after the teenager was involved in discipline cases. When Kanu got into a fight and was suspended for five days, Martin said, it prompted her to speak with the student and develop a rapport.

“Our relationship blossomed into something special,” Martin said. “I saw a change in her outlook on life. . . . I told her she can allow her situation to hinder her or let it help her become the person she wants to be.”

Last year, after a fight with her sister left Kanu with a serious bite wound and a trip to the hospital, Kanu moved out. Destitute and owing money for her hospital bills — and now completely on her own — she sought help, walking into social worker Marcella Fulmore’s office at Lee.

Fulmore helped Kanu start a new, independent life. She landed the job at McDonald’s on Backlick Road, where she worked behind the register, cleaned bathrooms and took out the trash. Fulmore helped her assume responsibilities well beyond her years.

“They are like my children,” Fulmore said. “They don’t have an adult as guidance, so I lead them every step of the way.”

Winland’s troubles began in the seventh grade, shortly after his father died of a heart ailment and complications from alcoholism.

The teenager began binge drinking and experimenting with drugs as a way to cope. During his freshman year, Winland was arrested after he and a group of friends broke into school concession stands to steal snacks. At the end of his junior year, Winland said his mother, a Christian with strict convictions, kicked him out of the house for lying to her about being sexually active. Attempts to reach Winland’s mother for comment were unsuccessful.

Winland lived on the streets and “couch-surfed” for a while, crashing at friends’ houses for a few days at a time until their parents hinted that he should move on. He survived on the kindness of friends who saw him losing weight and offered home-cooked meals. He once lived for a month in his girlfriend’s car, which he stashed in the Amtrak Auto Train parking lot in Lorton.

He took odd jobs to get by. He, too, ultimately sought Fulmore’s help, and she was able to arrange for him to qualify for free meals at school and gas cards from the county. For the time being, he lives with his girlfriend’s family.

“When I came in, I had a half-tank of gas and 12 bucks in my bank account,” Winland said. “They counseled me in stress relief, which helped me stay positive. Now I have three-quarters of a tank of gas and 17 dollars in my account.”

Kanu and Winland’s academic success is not typical for homeless students in Fairfax, as not all make it to graduation. Last fall, about 26 homeless students started the school year at Lee, including 10 seniors. By graduation day, only 11 homeless students remained at Lee, including four seniors. Some of the students switched schools or enrolled in more flexible programs to accommodate work schedules, others dropped out, and some disappeared entirely, officials said.

New beginnings await Kanu and Winland after graduation. Winland has decided to enlist in the Marine Corps and is scheduled to report to Parris Island, S.C. for training in September. He said part of his motivation to join the Marines was that he will be guaranteed a place to live.

Winland’s recruiter, Marine Staff Sgt. David Young, said that Winland’s homelessness helped prepare him for the military.

“We talk to applicants and try to get to know them on a personal level,” Young said. “We talked about some of his challenges and that for a while he was living on his own and making ends meet the best way he knew how. Based on what he’s learned from those challenges, it’s only made him stronger.”

Kanu plans to attend Norfolk State University with the assistance of scholarships and grants. She will be the first to attend college in her family, and she credits Fulmore and Martin with her success.

“I was lost,” Kanu said. “I didn’t know what I was going to do. But they helped me out a lot. Even though I don’t have the normal lives of other kids, I feel like I have because of all the support they gave me.”