Students arrived at Ethical Culture Fieldston, one of New York City’s most prestigious private schools, early Monday to find one of their classroom buildings locked. On the other side of a set of blue doors stood fellow classmates who had barricaded themselves inside, protesting what they said was a racist culture that Fieldston’s leaders had not done enough to reform.

By Monday night, some students were curled up in sleeping bags. On Tuesday, they were occupying the building for a second day as the head of their school was in crisis mode, trying to work with students and parents to end the lock-in.

Tensions at the school’s sprawling Bronx campus had been fomenting for weeks, after a video of students using the word “crack” followed by a racial epithet was shared among students and eventually seen by administrators. The video was created several years ago.

The administrators sprang into action after viewing the clip. Of the five students in the video, one had withdrawn from school, the school said. Three others were disciplined, and one student, who appeared unconscious in the footage, was not. None of those four students has returned to classes.

The head of the school, Jessica L. Bagby, scheduled meetings with students, parents and staff members in an effort to “create an enduring change in our school culture.”

But that was not enough for many students.

“I feel like our school can be a bit deceiving, because we do promote this mission of being dedicated to diversity, ethics, progressivism,” said Isabella Ali, a 17-year-old senior who helped organize the demonstration.

“Clearly, that’s not a true reflection of who we are. If anything, these incidents are a true reflection of who we are,” she added, referring to the video.

Fieldston, which has long prided itself on its progressive mission and experimental approach to combating racism, is now an epicenter of a citywide debate over how elite private schools, which serve mostly white and wealthy students, should handle race, class and prejudice.

Brooklyn’s private Poly Prep Country Day School also was the site of protests this year, after a years-old video of students in blackface resurfaced in January.

And Monday, students at Sarah Lawrence College, a small liberal arts school a few miles north of Fieldston, held a sit-in to protest what they called a racist campus culture.

Though some private schools have brought in anti-bias trainers and diversity officers in recent years, students of color have said they feel marginalized and misunderstood by peers and teachers. Fieldston is more diverse than many private schools: About 40 percent of its roughly 1,400 prekindergarten through 12th-grade students are not white.

The school is “really unwelcoming a lot of the time” to students of color, Chassidy Titley, a 16-year-old junior, said.

“We are often given obstacles where we are put into classes filled with only white teachers and white students.”

Naomi Habtu, also a 16-year-old junior, said she resented only being offered European and American history classes. “I applied because of the name Ethical Culture,” she said.

But, she said, the emergence of the video showed “how the school is straying more and more from that mission.”

Student organizers posted a list of demands on the building’s doors and online, seeking written apologies from the classmates involved in the video; a mandatory black studies course for high school students; and two students’ attendance at board of trustees meetings, among other requests.

They said the lock-in would continue until some of those demands were met.

Bagby said Tuesday afternoon that she wanted to stop communicating via email with the students and instead meet face to face. She also called a mandatory meeting for the parents of students who were planning to sleep at the school Tuesday night.

The protest, which started around dawn Monday, was organized by a group calling itself Students of Color Matter. It grew as other children skipped classes and joined in.

By midafternoon, protesting students lined the hallways and stairways of the administration building. When a teacher tried to enter, he found it barricaded.

By early Tuesday, dozens of teenagers said they were at a whiteboard, creating a plan for a second day of the sit-in.

Several parents have joined the lock-in during the day. In an email sent to families Monday, Bagby said she did not think it was “appropriate for parents, regardless of their position on this matter, to engage with students participating in the sit-in or choosing not to do so.”

On Tuesday, she sent another email, writing that the conflict arose “out of multiyear racial trauma our students have experienced while at our school. My colleagues and I could not be more profoundly sorry for this reality, which we fully recognize has weighed on the minds, hearts, and spirits of our students of color and their families for years.”

“We unequivocally honor students’ right to protest,” she added. “We must also provide for the rights of their peers to attend class.”

The demonstration is strikingly similar to a protest organized by Fieldston students in 1970. In March of that year, a group of mostly black high school students barricaded themselves in a building and called on the administration to hire more black teachers and staff members, and integrate black studies into the curriculum.

“We don’t want any more nice chats with the administration, we’ve had plenty of those,” said Mary Bassett, then a high school senior who went on to become Mayor Bill de Blasio’s first Health Department commissioner.

This article originally appeared in The New York Times.