A startling number of children in the United States are behind bars.According to the U.S. Office of Juvenile Justice and Delinquency Prevention, there were more than 54,000 offenders under the age of 21 in juvenile facilities on any given day in 2013, the most recent year for which data is available. And that number doesn’t include minors in adult facilities — on any given day in 2014, more than 4,000 people under 18 were incarcerated in adult jails. More than 16,000 of those were age 15 or younger Josie Whittlesey knows how harsh jail can be on children. She’s the founder and executive directorof Drama Club NYC , an organization that uses theater to mentor children incarcerated in these facilities.“There’s a lot of prison programs for adults, but there are not that many for youth. They’re very difficult to work with," Whittlesey said."They’re kids, so they’re hyper, and they’re hormonal. It’s a difficult population to work with, and it’s a really transient population to work with. But it’s incredibly rewarding and fun.”Drama Club NYC currently operates in three facilities in and around New York City: Crossroads Detention Center in Brownsville, Brooklyn; Horizon Detention Center in the South Bronx; and the Robert N. Davoren Complex for Adolescents on Rikers Island. They’re planning on expanding to serve girls soon.This month, they’ll be starting a pilot program at the Rose M. Singer Center on Rikers Island, the prison’s facility for juvenile girls.Refinery29 visited Drama Club NYC at Horizon Detention Center, where we spoke to Josie Whittlesey about her work with the program, and what she takes away from helping incarcerated teens grow through drama.This interview has been edited for length and clarity. Meredith Clark contributed additional reporting on this story.