Students at Mount Hebron High School in Ellicott City, Md., walked out of school on Tuesday, Feb. 2 after a student video disparaging the Black Lives Matter movement went viral. (Donna St. George/The Washington Post)

About 150 students at a Maryland high school staged a walkout Tuesday to show their opposition to racism after a white teenager at the school appeared in an online video disparaging the Black Lives Matter movement.

Leaving the building shortly after 10 a.m., students at Mount Hebron High School in Ellicott City gathered at the edge of campus and took turns delivering impassioned testimonies about their experiences with racism and their hopes for positive change.

“Stop the silence!” Lina Kebede, an 11th-grader, called out to the racially diverse crowd.

“Start the conversation!” the group called back.

Racial tension at Mount Hebron rose last week after a student was recorded making racist pronouncements in a 30-second video that was widely circulated online. The video shows the teenager saying, “who the [expletive] cares about some black man who dies?” Black lives don’t matter, the teenager said, because “they are an inferior race, okay?”

The video came to light during a week that Howard County’s schools were closed for snow. Classes at Mount Hebron resumed Monday, and at Tuesday’s walkout, students spoke with visible emotion about the power of words and the toll of racial discrimination.

One student said that when she was growing up, she tried to scrub her face of its brown color. Others talked about racial slurs and a lack of cultural understanding. Robert Jett, 17, noted that it was the second day of Black History Month and quoted Martin Luther King Jr. as saying, “Our lives begin to end the day we become silent about things that matter.”

The crowd cheered.

The protest was organized by a group of students — African American, white, Asian and Hispanic — who joined together after the video drew nationwide attention. Several community organizations and churches supported the effort, issuing a statement noting the damage that unaddressed racism can cause.

“When we don’t deal with the racism, these things are internalized and they have long-term effects,” said the Rev. Janelle Bruce, the youth pastor of St. John Baptist Church in Columbia.

Students at Tuesday’s demonstration stood in the 43-degree chill for more than 90 minutes as they addressed the crowd. Some had crafted statements. Others spoke spontaneously.

“We refuse to tolerate racism in our school,” said Sara Chernikoff, 16. “We are here to expose and demand an end to institutional racism within our school system.”

The students demanded more diversity in the school’s student government and mandatory ethnic studies classes to promote cultural awareness, and they called on teachers, staff and other school officials to denounce incidents of racism or hate speech.

“The message is to start a conversation about cultural awareness and understanding,” Zakariya Kmir, 16, a senior and president of the county’s Alpha Achievers, a program that fosters a positive learning environment for black male students. “It’s not just race.”

John White, schools spokesman in Howard, described the students’ requests as “thoughtful and reasonable.”

Howard school officials said the student who made the racist statements in the video has not returned to school, pending the outcome of a school investigation and a meeting with him and his parents. School officials have identified a total of four students involved in the video.

The walkout came five days after the school system’s superintendent, Renee Foose, sent a letter home to families saying that the video offended “many people of all races” and reflected poorly on the students involved and “those who chose to stand silent.”

“The behavior is unacceptable and will not be tolerated,” she wrote.

The student who made the racist remarks posted an apology on social media last week. Efforts to reach the student and his family have been unsuccessful.

Racial issues are not new to the high school, where whites make up the single largest racial or ethnic group, at 49.8 percent last year. Some students said that an area of campus where black students often gather is called “the jungle” and that it is not uncommon to hear white students use racial epithets in school hallways.