LEESBURG, Va. — Long before the father was tackled by sheriff’s deputies at the school board meeting, before there was shouting to reopen classrooms and before “parents matter” became the central slogan of the most closely watched campaign in the post-Trump era, Loudoun County was just another American suburbia taking a hard look at its schools.

The county, at the edge of the Virginia sprawl outside Washington, had grown much more diverse. White students were no longer in the majority, and educators were trying to be more aware of how racism could affect their students’ education.

The district hired a consulting firm to help train teachers about bias. It tried to hire more teachers of color. And a high school changed its mascot from the Raiders, named for a Confederate battalion, to the Captains.

But there were rumblings of resistance.

Vocal parents protested the district’s antiracism efforts as Marxism.

Some teachers disliked the trainings, which they found ham-handed and over the top.

And evangelical Christians objected to a proposal to give transgender students access to the restrooms of their choice — complaints that were magnified when a male student wearing a skirt was arrested in an assault in a girl’s bathroom.

Within a year, Loudoun County had become the epicenter of conservative outrage over education. Several hundred parents, in a district of 81,000 students, managed to pummel their school board and become a cause célèbre for opposing the district’s handling of race and gender issues.

Along the way, they got plenty of help from Republican operatives, who raised money and skillfully decried some of the district’s more aggressive efforts, even buying an ad during an N.F.L. game.

The media also jumped in, feeding the frenzy. The story rebounded from one outlet to another, with conservative media leading the way, from The New York Post to The Daily Wire to Fox News, which aired 78 segments on the racial issues at Loudoun schools from March to June this year, according to Media Matters, a left-leaning group that scrutinizes media coverage.

By November, these skirmishes had been transformed into a potent political movement — parents’ rights — that engulfed the state’s schools and the governor’s race. The Republican candidate, Glenn Youngkin, successfully tapped into the fury, adopting the slogan “parents matter.”

“Glenn became a vessel for their anger,” said Jeff Roe, the founder of Axiom Strategies, Mr. Youngkin’s campaign consultant.

The campaign identified early on, he said, that education was a key issue that could make inroads in Democratic strongholds. Mr. Youngkin’s opponent, the former governor Terry McAuliffe, won Loudoun County, but by a far narrower margin than President Joe Biden had won last year.

Ian Prior, a Republican political operative who lives in the county and has been at the center of the fight, called education the “one unifying issue out there that kind of gets everybody.”

Now, Republicans and Democrats are dissecting how these educational issues can be used in the midterm elections next year.

Loudoun may well be their case study.

A District, Struggling With Change

In the not-too-distant past, Loudoun County was dominated by farmers and Republicans. In recent years it has experienced a wave of residential growth to 420,000 people, becoming more suburban, increasingly diverse and, at the same time, more liberal.

The student body has changed, too. Twenty five years ago, 84 percent of the students were white; today, 43 percent are, owing partly to an influx of immigrants working in technology jobs. Currently, 7.2 percent of students are Black.

The shift hasn’t been easy. In 2019, for example, an elementary school asked students, including a Black student, to emulate runaway slaves during a game mimicking the Underground Railroad, drawing criticism from the local NAACP.

Parents also said they encountered racist treatment, both subtle and overt. Zerell Johnson-Welch, who is Black and Latina, moved to the district in 2008 with her husband and three children.

One day, her daughter came home upset, she said.

“She was in an advanced math class,” Ms. Johnson-Welch said. “A kid yelled out, ‘Why are you in this class?’” — using a racial epithet to emphasize that she did not belong.

Loudoun County commissioned a study by a consulting firm, the Equity Collaborative, which bore out such stories, concluding that Black, Hispanic and Muslim students had been the focus of racial slurs and that Black students were disciplined more frequently than others.

Loudoun set out on a plan. In addition to changing the high school mascot, the school system released a video apologizing to Black residents for past racial discrimination. The schools devised a protocol for dealing with racial slurs and other hate speech. And teachers underwent training in cultural sensitivity.

There was backlash.

Some teachers objected to a chart in their training that listed different groups as either “experiences privilege” or “experiences oppression.” Christians were privileged, for instance, while non-Christians were oppressed.

Monica Gill, an American history teacher at Loudoun County High School, also objected to an animated video called “The Unequal Opportunity Race,” in which white people get a head start, while people of color must wait and then face obstacle after obstacle.

The video, she said, was an overgeneralization that itself embraced a racial stereotype.

“I didn’t grow up in white privilege,” Ms. Gill said. “I worked hard to get through college, and it wasn’t handed to me by any stretch. It seemed to me that this whole thing they were pushing was very shallow.”

Mr. Prior, a former Trump administration official with two children in the district, wrote a piece in October 2020 for The Federalist, a conservative outlet, in which he raised questions about what he called the “supercharged” antiracism effort.

But Beth Barts, a former school board member, said the effort was worth it.

“Whites are now less than half our student population,” she said. “It was important that we recognize that, and we teach that other voices should also have a place at the table.”

Some people don’t like that, she added. “They felt threatened.”

The pandemic did not help ease anxiety. The state’s schools were slow to reopen, and parents became increasingly agitated, concerned that virtual learning was harming their children, academically and emotionally.

At a school board meeting in January 2021, Brandon Michon, a father of three, lined up with about 50 other parents to argue that in-person classes needed to resume.

“You should all be fired from your day jobs,” Mr. Michon practically yelled into the microphone. “Figure it out or get off the podium.”

His diatribe went viral, with an assist from Fox News, where he became a repeat guest.

Weeks later, Mr. Prior learned that his name had been placed on what he viewed as a sort of “enemies list” by a Facebook group called “Anti-Racist Parents of Loudoun County,” he said in an interview.

The list, he said recently, led him to form Fight for Schools, a political action committee.

Mr. Prior promoted his cause nationally, becoming a frequent guest on Fox News, including “Tucker Carlson Tonight.”

Mr. Prior also began efforts to recall several school board members, including Ms. Barts, a former school librarian who had joined the Facebook group.

By May 2021, Mr. Prior’s political action committee had launched an ad that referred to the teacher training materials, warning that Loudoun schools were instructing teachers that Christians are oppressors.

Teachers and administrators said that conservative activists had cherry-picked the most extreme materials to try to prove their point, but some educators also acknowledged that some of the training was over the top, including the “experiences oppression” chart. A spokesman for Loudoun County schools said that chart is no longer used.

Many teachers are also quick to defend the training. One of them, Andrea Weiskopf, said that part of the idea was to raise awareness that students from different backgrounds could perceive literature and events differently.

As a result, Ms. Weiskopf said, teachers would realize that the “Norman Conquest” might be viewed as the “Norman invasion,” depending on one’s perspective. Manifest Destiny, the idea that the westward expansion of the United States was intended by God, is another example.

“It can help students understand that everything has another side,” Ms. Weiskopf said. “What made America from sea to shining sea came with a price to Indigenous people.”

But white parents weren’t the only ones concerned about Loudoun’s plans. In August 2020, the school board adopted new admissions policies for two selective high schools, to try to bring in more Black and Latino students. More than three dozen parents, mostly South Asian, filed suit against the district, which was eventually dismissed.

A Rape, a False Story and Transgender Rights

During the spring, the Loudoun County School Board meetings grew hostile and vitriolic, sometimes almost unmanageable. The district was forced to hire extra security and set up a staging area outside for media interviews.

Tanner Cross, a gym teacher, took the podium in May to speak on another divisive topic: a proposal permitting transgender students to use the restrooms and pronouns of their choice.

“I will not affirm that a biological boy can be a girl and vice versa because it’s against my religion, ” Mr. Cross said. “It’s abuse to a child. And it’s sinning against our God.”

Mr. Cross was placed on leave by the school system.

In late June, 259 parents lined up to speak at a school board meeting, many to defend Mr. Cross. But others supported the new policy.

One was Kellie Herring, who identified herself as “a proud screaming parent of a young transgender son in the Loudoun County Schools.”

“Today,” she said, “instead of focusing on the hate that seems to be dripping from the followers of Jesus in this room and from their kids in our schools …”

Ms. Herring was unable to complete her sentence; the crowd broke into jeers and boos, and the meeting went into recess.

Later, at the back of the room, Scott Smith was arrested and charged with disorderly conduct after getting into a scuffle. He had been upset because his 15-year-old daughter had been sexually assaulted in a high school restroom by a 14-year-old student, identified by Mr. Smith as a “boy wearing a skirt.”

The incident played into the fears of some parents about the new transgender bathroom policy.

Conservative media outlets zeroed in on the transgender angle; Fox News aired 88 segments in just over three weeks, according to an analysis by Media Matters.

The events turned out to be different than originally cast.

At a juvenile court hearing, it was revealed that the two students had an ongoing sexual relationship and had arranged to meet in the bathroom. The crime, which took place before the transgender policy went into effect, was not a random assault.

But the narrative had been set.

By September, with the governor’s election in the final stretch, Mr. Prior’s group had raised nearly $300,000 from around the country. Among the major donations was $10,000 from 1776 Action, an anti-critical race theory organization formed in March.

In September, at a Save Our Schools rally in Loudoun County, Mr. Youngkin repeated his vow to abolish critical race theory in Virginia. The phrase, which originated decades ago as an academic concept, has become a conservative rallying cry, used to broadly criticize educational and social efforts to address racial inequalities in education.

A debate in September further inflamed many parents, when Mr. McAuliffe, the Democratic candidate for governor, said, “I don’t think parents should be telling schools what they should teach.”

That same month, Ms. Barts, the school board member, was surprised to see her photograph in a television ad attacking Loudoun schools and broadcast during the Washington Football Team’s season opener.

It was paid for by the “Free to Learn Coalition,” which is tied to Leonard Leo, a prolific fund-raiser and confidant of President Trump. Mr. Leo serves as co-chairman of the conservative Federalist Society.

Ms. Barts, who resigned from the board this month amid the recall fight, views the year’s events as a harbinger of things to come.

“I don’t think it’s going to stop,” she said. “I think this is going to be seen as an effective way to bring out voters.”

As if to prove her prediction, Mr. Prior was one of about 100 parents who spoke at a school board meeting on Tuesday night, where he announced a plan to recall Brenda Sheridan, the board’s chairwoman.

“We’re still here, and we’re not going anywhere,” Mr. Prior vowed.

Sophie Kasakove contributed reporting from New York. Kitty Bennett contributed research.