TULSA, Okla.—For decades, Oklahoma students weren’t required to learn about the Tulsa Race Massacre in school, in what the city’s school superintendent called a “conspiracy of silence.”

Now some residents and educators worry that a new state law could derail progress in teaching about the tragedy, in which white mobs burned much of the Black community of Greenwood to the ground a century ago, leaving as many as 300 people dead.

The law, signed by Republican Gov. Kevin Stitt on May 7, restricts public-school teachers and employees from using lessons that make an individual “feel discomfort, guilt, anguish or any other form of psychological distress on account of his or her race or sex.”

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A view of Tulsa’s Greenwood neighborhood. Shane Brown for The Wall Street Journal

Days later, Gov. Stitt was ousted from the 1921 Tulsa Race Massacre Centennial Commission, which said his action was contrary to the group’s mission. The commission called his approval of the legislation “a sad day and a stain on Oklahoma.”

Similar legislation designed to counter moves by school districts to focus lessons on race or systemic racism has been passed in Idaho and Tennessee and is being considered in at least a dozen other states. Some of the Republican-backed legislation specifically bans a decades-old teaching method called “critical race theory,” which addresses the way racism is embedded in laws and society.

Educators have been more focused on race and racial inequities after a year of civil unrest following police killings of Black people. In April, the U.S. Department of Education outlined its proposed priorities for grants for American history and civics education, with applicants asked in part to indicate how they would take into account “systemic marginalization, biases, inequities, and discriminatory policy and practice in American history.”

Some Oklahomans criticized Mr. Stitt’s timing in signing the bill into law just weeks before the 100-year anniversary of the massacre on Monday. Opponents say that while the law doesn’t forbid teaching students about the massacre, it is an attempt to stifle lessons that deal with unpleasant aspects of history.

“This is a way to keep the history of Tulsa in the dark, in the closet,” said Jennettie Marshall of the Tulsa school board. “It has been a dirty little secret.”

The Oklahoma Council of Public Affairs, a conservative think tank, applauded the legislation. “From a government perspective, should taxpayers be required to pay the salaries of government employees to teach that whites are inherently racist or inherently privileged? I think the answer would be no,” said Jonathan Small, president of the group.

Oklahoma Gov. Kevin Stitt was ousted from the 1921 Tulsa Race Massacre Centennial Commission after he signed a bill that critics say will discourage lessons on the history of the tragedy.

Oklahoma Gov. Kevin Stitt was ousted from the 1921 Tulsa Race Massacre Centennial Commission after he signed a bill that critics say will discourage lessons on the history of the tragedy.

Photo: Sue Ogrocki/Associated Press

Some educators said that teaching about the massacre in Oklahoma schools has gotten better in recent years. In 2019, state academic standards required for the first time that Oklahoma history classes include in-depth lessons on the massacre, including the “emergence of ‘Black Wall Street’ in the Greenwood District” and the “causes of the Tulsa Race Riot and its continued social and economic impact.” The standards also include an opportunity to introduce the massacre in broader terms to second-grade students, but it isn’t required.

“I did not learn about the Tulsa race massacre until I was an adult,” said Joy Hofmeister, Oklahoma’s education chief, who grew up in Tulsa. She supports more detailed lessons about the massacre: “We have to face the historic events of that time and learn critical lessons from that.”

Oklahoma Sen. Rob Standridge, a Republican and co-author of his state’s bill, warned parents about school lessons in a statement. “I encourage every parent to make certain their schools aren’t making some students feel that, solely based on the color of their skin, they are naturally racist, they are inferior or superior,” said Mr. Standridge.

James Taylor teaches seventh grade in Oklahoma City and said the new law addresses those who cross the line. “It doesn’t say you can’t talk about racism; you just can’t say all white people are racist,” said Dr. Taylor.

Some teacher groups are concerned that the law puts their members in a difficult position. “Our teachers are mostly worried about what will happen to them legally with their job, or legally with themselves, in a civil lawsuit if they teach anything related to diversity or race,” said Torie Shoecraft, president of the Oklahoma City American Federation of Teachers, which has about 1,500 members.

Students in a physical education class at Booker T. Washington High School in Tulsa, May 14. This month, Tulsa Public Schools rolled out a new curriculum to teach about the 1921 massacre.

Students in a physical education class at Booker T. Washington High School in Tulsa, May 14. This month, Tulsa Public Schools rolled out a new curriculum to teach about the 1921 massacre.

Photo: Trent Bozeman for The Wall Street Journal

Stefanie Wager, president of the National Council for the Social Studies, an association of about 10,000 teachers and other social studies professionals, questioned how states will monitor educators for compliance with the new laws focused on race, especially as interest grows in teaching on the subject.

Todd Gragg is a teacher for Seminole Public Schools, a small district about an hour from Oklahoma City. He said that while he has concerns about how the law might affect teaching about the massacre and racism in his Advanced Placement U.S. history and government classes starting in the fall, he plans to do so anyway.

The Tulsa Massacre of 1921 destroyed hundreds of Black-owned businesses and homes in the city’s Greenwood District. A century later, entrepreneurs and activists are working to preserve “Black Wall Street’s” memory while pushing to rebuild and recover what was lost. Photo: Rob Alcaraz/The Wall Street Journal The Wall Street Journal Interactive Edition

“Are we going to run from the truth or be willing to teach it openly in the classroom?” said Mr. Gragg. “The reality is there is structural racism. We can’t deny that it exists.”

Research shows that U.S. history classes from kindergarten to 12th grade devoted about 9% of their time to Black history in 2015—and not much has changed since then, said LaGarrett King, an associate professor of social studies education at the University of Missouri. Part of the issue is that while teachers have been willing to teach Black history, some don’t know it themselves. “The average teacher means well,” Dr. King said. “But there is a lack of knowledge. A lot of these teachers were educated in the same system they are educating in.”

Booker T. Washington High School was founded in 1913 as Tulsa’s first high school for Black students.

Booker T. Washington High School was founded in 1913 as Tulsa’s first high school for Black students.

Photo: Trent Bozeman for The Wall Street Journal

Oklahoma school districts are weighing in on the new state law. The school board of Oklahoma City Public Schools, the state’s largest district, approved a resolution denouncing the legislation. Tulsa Public Schools, the state’s second-largest district, said the law has no implications for how it teaches about the massacre. Tulsa officials rolled out a new curriculum on the massacre this month for grades three through 12.

“This is history that is painful, but our approach is firmly grounded in the belief that one human being isn’t ‘worth’ more than another,” the Tulsa district said in a statement.

Mr. Stitt has said the Tulsa Race Massacre can be taught under the new law, which he noted doesn’t prohibit teaching concepts aligned with state academic standards. The law also forbids state colleges and universities from requiring students to engage in any form of mandatory “gender or sexual diversity training or counseling.”

But the centennial commission, which removed Mr. Stitt as a member, said in a statement that while the law doesn’t preclude teaching about the Tulsa Race Massacre, it clearly intends to limit teaching the racial implications of America’s history.

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After the legislation was signed, the commission invited the governor to attend a special meeting to discuss the bill. Mr. Stitt didn’t show up or reply to the invitation, the commission noted in a May 11 letter to the governor. The letter said he could contact the group for discussion, but not doing so would indicate further disavowal of its goals and an official resignation. On May 12, the commission met and decided to part ways with Mr. Stitt, according to a statement from the group.

Mr. Stitt said in a statement that his role on the commission was ceremonial and accused the group of sowing division based on falsehoods.

Despite the tension over the law, some parents are looking forward to their children learning about the massacre. Tulsa parent Michelle Lamb gave her 10-year-old daughter, Annette, a lesson on the massacre a few days before she was to start learning about it in school. The mother and daughter spent time earlier this month reading placards embedded in sidewalks on Greenwood Avenue, which show where businesses stood before the massacre, whether the owner died and if the business reopened.

“I can try to teach her, but it’s best to show her,” Ms. Lamb said.

Write to Tawnell D. Hobbs at Tawnell.Hobbs@wsj.com