Students at Wadleigh Secondary School for the Performing Arts in Harlem stampede out of their classrooms. A sea of blue and orange, gold and maroon, and white uniforms fill the halls as students from three different schools travel to their next classes. They share a gym, auditorium and cafeteria, but each school starts and ends at a slightly different time.

This fall, Wadleigh gave up one of its floors to Harlem Success Academy. Wadleigh, on West 114th Street, had already relinquished two of its five floors to Fredrick Douglass Academy II for the past seven years.

Three is a crowd, at least according to some students and teachers at Wadleigh and Frederick Douglass. Co-location, which refers to two or more schools occupying a single building, has become prevalent in Harlem and other New York City neighborhoods.

“The New York City Department of Education has been much more aggressive in exploring and mandating co-location than in almost any other district in the country,” said Jeffrey Henig, a political scientist and education professor at Columbia Teachers College. “In most places, charter schools have to find their own facilities.”

Although both Frederick Douglass and Harlem Success co-exist in the building Wadleigh initially had to itself, each school occupies a different floor. Harlem Success even uses a separate entrance. But space becomes an issue when students transition to their next class.

One student noticed the cramped hallways and stairwells within his first few days at Frederick Douglass. “It’s kind of hard because you have to travel up and down the stairs, and you got the high schoolers traveling, too,” said Jahqwan Gilford, a sixth grader.

Last winter, Wadleigh parents and administrators fought to keep its middle school open after it received a D on its Department of Education progress report, even importing Princeton professor Cornel West to defend Wadleigh. Some suspected that the Department kept Wadleigh open so that Harlem Success could move in. (The Department of Education didn’t respond to requests for comment.)

“Typically, we see charter schools expand in places where traditional schools have been underperforming for a long time,” said Andrea Rogers, policy director of New York Charter Schools Association. “Schools aren’t considered for co-location unless they’re being underutilized.”

One thing is certain: with co-location, both district and charter school teachers must learn to cope with limited space.

Some teachers have to move out of their classrooms frequently because they share their rooms with several people.

“Teacher space is limited,” said a Wadleigh middle school teacher, who wished to remain anonymous. “Sharing classrooms limits us from hanging up students’ work or grading assignments right after class. Because once you’re finished teaching, someone else comes in.”

This teacher shares two classrooms on the first floor with three other teachers and doesn’t stay in any classroom for more than one period.

Charter school teachers agree that space is limited in their classrooms and offices. KIPP Infinity, a charter school, has an elementary, middle and high school in the same building as New Design Middle School, a Harlem district school on West 133rd Street.

Ample classroom and office space is a luxury that KIPP, like many charter schools, can’t afford as it expands. Julia Lee, a KIPP Infinity speech and language coordinator, said this is a common problem. She is thankful to have her own office to provide therapy.

“Our schools are growing,” Lee said. “In KIPP Infinity Elementary, for example, a whole new kindergarten class came in this year. But Infinity Middle sacrificed one of its classrooms to the elementary school. Space is really, really tight.”

Charter schools often can’t afford new buildings. The Department of Education gives them money to hire staff and buy materials, but they are on their own when it comes to infrastructure and facilities, Rogers said.

“The idea is that the charter school should be receiving roughly the same amount that the district does on the operating cost,” she said.

Rogers added that debt, transportation and some other items aren’t included in the grants given to charter schools.

Although charter schools don’t receive public funds to establish their own buildings, they can use private funds to revamp their space. Harlem Success Academy’s décor livens up its newly-renovated fifth floor. It decorates classroom walls with college-readiness messages and drapes doors in banners from prestigious colleges. The nameplates outside classrooms identify not just the teachers’ subjects but their alma maters. The fifth floor also has considerably newer bathrooms than the rest of the building.

“With all that money, they should get a new school,” the Wadleigh middle school teacher said.

Nevertheless, some charter school parents advocate co-location. Dana Broom, mother of a Harlem Success fourth grader, said co-location can motivate students to accelerate their learning.

“I don’t see the big deal for pushing them out,” Broom said. “If you ask me, they should turn all the schools into charter schools.”

Frederick Douglass mother Claudette Abney said she knows the school is crowded, but so far, her son hasn’t complained. She said it’s still too early in the school year to tell how co-location will impact her child.