Using the accepted social metrics of teenagers in this country, Thakane Masondo should have plenty of friends.

She is in the second semester of her senior year at Frederick Douglass Academy in Harlem. She plays lacrosse, belongs to the global history club and is the founder of a dance group that performed at the Apollo Theater. She has a playful sense of humor and a mischievous smile.

The truth, though, is that Ms. Masondo does not have many friends  by choice. Having more, she reasons, would mean more people knowing her secret.

“I live in a homeless shelter,” Ms. Masondo said. Tears appeared in her eyes as she revealed how she pretended to have a home to return to after school, a family to look after her. “I can’t really have any friends.”