The questions came at a June 8 meeting with the Mystic Valley trustees, where 15 speakers raised the issues, describing a culture that penalized students who spoke out about inequities, while seeming to shrug off reports of bias. They also demanded to know why a series of controversial social media posts made by a cofounder of the Malden charter school hadn’t been publicly denounced.

“It’s going to take somebody to get their hands dirty, really going in and really, really, really looking this horrible situation in its eye,” Alvin Buyinza, a 2015 graduate, told the board. “There is a conversation on race that needs to be addressed at the school level.”

Amid a nationwide outcry on racial injustice, an urgent chorus of voices is calling for change at Mystic Valley, a K-12 charter school ranked in April as the sixth best high school in the state by U.S. News and World Report. One alumni group gathered hundreds of signatures on a petition demanding a more diverse faculty and a restructuring of the school’s mission statement to “address issues of systemic discrimination.” Another group said it has compiled more than 150 examples of alleged incidents of racism and LGBT bias. On June 25, parents and students held a protest, waving signs as drivers honked their horns.

“The culture has to change at the school,” said Zane T. Crute, president of the Mystic Valley area branch of the NAACP, who sent a scathing letter to administrators endorsing the petitioners’ demands. For change to happen, he said, an independent evaluation of policies must be conducted “to keep the school honest — separate from the donors, separate from the board.”

Few would deny that Mystic Valley, which was founded in 1998 and enrolls more than 1,550 students from Malden and surrounding communities, provides strong education to a diverse student body. Sixty-one percent of seniors in 2019 earned the John and Abigail Adams Scholarship. While most schools in Massachusetts require 180 days of instruction, Mystic Valley tops out at 200.

But the school also has an unsettling track record on issues of race and inclusion. Recent data shows Mystic Valley disciplines Black and Latinx students at sharply higher rates than white students, and disabled students at a higher rate still.

In 2017, in a widely publicized move, Attorney General Maura Healey determined a school policy that banned hair extensions and other hairstyles discriminated against students of color, especially Black students, who’d been suspended and banned from activities. Two years earlier, regulators pushed back on efforts to increase enrollment because the school lacked proper services for non-English speakers. And when a student wanted to form a gay-straight alliance club in 2014, her efforts were stymied until the American Civil Liberties Union got involved.

A series of social media posts made by Neil Kinnon, a Mystic Valley cofounder and former Malden city councilor, has sparked the latest conflagration. As protests swelled after the killing of George Floyd, a Black man, by a white police officer, Kinnon posted a Wall Street Journal opinion piece titled “The Myth of Systemic Police Racism.”

“Please consider the real facts not the propaganda,” he wrote on his “Kinnon For Malden” Facebook page, a screenshot of which was obtained by the Globe before it was taken down. Systemic racism, he commented, is “a false narrative” and “the millions marching are indeed pawns.” Kinnon did not respond to e-mails and phone calls for this story.

The backlash to the Facebook post was swift. Students, alumni, even one of Kinnon’s neighbors blasted his statements. Meanwhile, screen shots of additional posts allegedly made by Kinnon on other Facebook pages triggered further outrage.

Long a divisive figure in Malden, Kinnon resigned from the charter school’s board of trustees in 2019 and no longer holds an official role there. But students say his influence is still felt. Petitioners asked that the school “further disaffiliate” from him by ending the Neil Kinnon Citizenship Award, presented annually to a graduating senior. And Alfie Tsang, 2020 class president, pushed trustees for clarity on Kinnon’s connection to the school, and why they hadn’t condemned the social media posts.

Chairman George Warren said at the June 8 meeting that the board was aware of Kinnon’s statements but needed time to “digest” things. “We will get back to you and the public,” he said, “if it’s deemed necessary.”

On June 16, Warren and Alexander Dan, the school’s superintendent/director, released a letter to parents. In it, they said Mystic Valley had undergone an “expansive internal investigation” in 2017 after the attorney general’s investigation. They’d “voluntarily implemented” suggestions from the review, which was conducted by a third party. Staffers received implicit bias training. Efforts to recruit more teachers of color were ongoing.

They also invoked George Floyd and condemned “the unacceptable tolerance of racism by sections of our society.” There was no mention of Kinnon.

In response to calls and e-mails from the Globe, Dan forwarded an annotated version of the letter to parents that was sent separately to the alumni behind the petition. There, Dan did refer to Kinnon: “Respectfully, we will not address the conduct of any person who is not a board member and not an employee at the school.”

Dan further noted: “Prior to your letter, Mr. Kinnon had already voluntarily determined to suspend his citizenship award at the school.”

Parents and students say the problems at Mystic Valley run much deeper than offensive social media posts. They say marginalization is baked into the foundation of the school, starting with its mission statement. It describes a “world class education characterized by a well-mannered, disciplined and structured academic climate” based in the “fundamental ideals of our American Culture.”

But how that discipline is delivered, and to whom, has left many frustrated, particularly when it comes to students of color.

“What they purport as discipline is essentially authoritarianism,” said Eric Henry, a retired Navy veteran and father of triplets going into ninth grade. Henry, who is Black, described several encounters his children have had, ranging from microaggressions to disciplinary incidents. In one, his daughter Thora was pulled out of class and reprimanded by a white teacher she did not know because she had dropped off a book in a classroom without knocking.

“She’s experiencing harassment and conflict resolution at way too young an age,” said Henry, who served on the PTO for several years. If parents complain about the way their children are treated, “They say, ‘Don’t forget, you asked to come here.‘ ”

Thora added: ”If you’re a student of color, you won’t get the benefit of the doubt.”

Indeed, data provided to the Department of Education showed that of the 289 Black students enrolled at Mystic Valley in 2018-19, 34, or 11.8 percent, received some sort of disciplinary action. Of 151 Latinx students, 17, or 11.3 percent, were disciplined. By comparison, 49 of 762 white students were disciplined, or 6.4 percent. Dan could not be reached for comment on the DOE numbers.

By far the highest percentage of disciplinary action was taken against students with disabilities. Of 221 students identified as having disabilities that year, 44, or 20 percent, were disciplined.

Parents and students also raised concerns about what they see as a pervasive insensitivity toward students with multicultural backgrounds.

Vanessa Santos described a situation in which her daughter, a rising eighth-grader, was chastised by a teacher who told her to stop “speaking Spanish.” When the girl noted that she was speaking Portuguese, she said, the teacher waved her off, saying, “It’s all the same.”

Kedisha Clerger, a 2019 graduate who now attends Howard University, described a painful experience from her senior year. One day on her way to class, she was speaking to a friend about college applications, confiding that she’d thought about writing an essay “comparing Mystic Valley to slavery.”

A teacher who’d been eavesdropping broke into the conversation. “I guess you could compare me to a plantation owner,” she recalled him saying.

Stunned, Clerger reported what had happened to administrators. And there began a head-spinning series of events. She was told the teacher was “just making a joke.” She was told she bore responsibility, that if she hadn’t made the slavery comment, the teacher wouldn’t have responded that way. Dan could not be reached for comment on the incident.

When all was said and done, Clerger said, she was accused of being “rude and disrespectful” and was suspended for a day.

“You report stuff at the school and they try to silence you,” she said. I just felt hopeless.”

Clerger recently wrote about the experience, posting it to the Mystic Valley Parents Facebook page. She said God has been a source of strength as she looks back on her time at the school. And she urged the community to take action.

“Black kids at MV go through so much that is unknown to people,” she wrote. “Fight for change.”