Mr. Starks had a hard time, too: “The first night I cried — a young adult in college on my own.” But he also said, “I don’t let brokenness get in my way; I’ve always known if I worked hard, doors would open.”

The biggest door so far opened in the spring of 2011, when he was accepted to U.C.L.A. For Mr. Starks, it was validation that he was the kind of person he’d believed himself to be.

“To celebrate,” he said, “they had a dinner for me at the group home.”

Last summer, living in a dorm was not so hard because by then Ms. Boccara and Mr. Starks had become friends. Ms. Boccara is pretty sure her roommate during the school year has a sense of her background but not the details. “She hears me on the phone, but I don’t talk about it,” Ms. Boccara said. “The only person I tell is Kaleef.”

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THINGS are harder at Los Angeles City College.

Nearly three-quarters of the students qualify for an annual tuition waiver because they are too poor to pay the $1,400. The average age is 30, meaning many have probably failed at college before. The graduation rate is only 6 percent within six years (versus the national community college average of about 14 percent in three years).

City College, like most community colleges, does not have dorms, and most students find housing through social welfare agencies. Mr. Roque lives in housing financed by First Place for Youth, a nonprofit organization that serves former foster children. He was 18 when he left the last of seven homes, in 2010, and as is true for many foster youth, there are pieces of his story he doesn’t know. He was too young to remember why he was removed from the first two homes. Another house was closed for violations. His fourth foster mother planned to adopt him, he said, but changed her mind.

Last spring, Mr. Roque was rejected by Los Angeles City College for having failed to make adequate academic progress; he says he had twice attended area community colleges, but withdrew without earning any credits. To be reconsidered, he had to write a letter of appeal explaining any mitigating circumstances, which in Mr. Roque’s case was homelessness.

He wrote of the transition from foster care to no care: “Couch surfing, from relatives who did not like me to friends who got tired of me. I was not able to concentrate in school or even keep my grade-point average at a 2.0.” He also filled a single-spaced page with several more mitigating circumstances and in his conclusion promised to do better: “I have such a good support system in place, people who expect a lot from me, and I am in a place where I can make school a priority. I am serious this time.”