Her name won’t appear on the ballot. Most voters have no idea who she is. But Catherine Lorenze, a sharp-tongued parent activist and Republican strategist, wields uncommon influence in the race for the Fairfax County School Board.

Half of the board’s 12 members are retiring, ensuring high turnover among those who set the direction of one of the country’s largest, highest-performing school systems.

Most of the candidates promising dramatic change are running under Lorenze’s tutelage, echoing messages she crafted about transparency, accountability and fiscal responsibility.

A McLean mother of three, Lorenze accuses the board of ignoring input from parents and teachers on student-discipline reform and other hot-button issues. She contends that the board’s oversight of Superintendent Jack D. Dale has been toothless and that it has unfairly allowed class sizes to balloon in wealthy neighborhoods (including her own) while schools in poor areas get more resources.

Much of Lorenze’s work is behind the scenes: writing campaign plans, analyzing election records, organizing volunteers. But she also broadcasts her views on her blog, Red Apple Mom, where she writes about incumbents she wants to depose.

Chief among her targets are Chairwoman Jane K. Strauss (Dranesville) and Vice Chairman Ilryong Moon (At-Large).

“Grandmother Janie Strauss is in her second decade on the School Board. Snooooozzzzzzeeeeee. Can’t she go do something else already?” Lorenze wrote in June. “Ilryong Moon — the human weather vane who can’t cast a vote until he sees which way the political winds are blowing — was first elected in 1995. Can’t he go do something else too?”

Moon, who said he is proud of his record as a deliberate thinker, shrugged off the attack. “I cannot get upset by one person’s personality,” he said. Strauss, an 18-year board veteran facing a tough reelection battle against Lorenze-backed candidate Louise Epstein, was more pointed.

“Catherine seeks out the divisive issues and then plays on them,” Strauss said. “If her candidates win, that’s the voice. Is that the voice we want in Fairfax County?”

Elizabeth Schultz, a Republican-endorsed candidate in the Springfield district, said that Lorenze helped her devise slogans and plan logistics early in the campaign. Lorenze has played less of a day-to-day role in recent weeks, Schultz said. “Once I got rolling, honestly, I sort of ran with it,” she said.

Megan McLaughlin, a Democratic-endorsed candidate for the Braddock seat, said she was “fortunate” to have early guidance from Lorenze “in how to get through a campaign cycle like this.” But McLaughlin said she has many other advisers as well.

Lorenze is managing the campaigns of Epstein for the Dranesville seat and Lolita Mancheno-Smoak for an at-large seat. She is also helping Sheree Brown-Kaplan and Steve Stuban in their at-large bids. Stuban has no partisan endorsement. The other three are Republican-backed. The School Board election is officially nonpartisan, but party politics often play a role.

In all, Lorenze has donated to various candidates services worth more than $80,000, according to financial disclosure forms — a substantial amount for down-ballot races usually run on the cheap.

Lorenze learned how to shape a sound bite while working on campaigns with Republican consultant Mike Murphy during the 1990s, helping to produce ads for high-profile figures such as Sen. John McCain (R-Ariz.) and former New Jersey governor Christine Todd Whitman (R).

In Fairfax, she helped run successful special-election School Board campaigns in 2009 and 2010 for Patty Reed (Providence), a Republican-endorsed member, and Sandy Evans (Mason), a Democratic-endorsed member. Reed and Evans, both known for challenging the superintendent, are running unopposed for reelection.

Lorenze said she has a personal stake in the election. Her son had 30 classmates in fourth grade and 35 in fifth, and Lorenze said that was unacceptable.

“I get one shot with my kids,” she said. “I’m not willing to wait for class size to normalize in 10 years. I’m impatient.”

Lorenze, 44, was a traditional school volunteer until five years ago, when she organized parents to raise questions about issues at Kent Gardens Elementary. She was asked to leave her post as room parent. Her agitations for change “had an overwhelming impact on the instructional day,” Principal Robyn Hooker said.

Months later, Lorenze was also fired from her volunteer PTA post. “Circumstances have made it necessary to end your appointments,” read a certified letter delivered to her home.

She joined Fairgrade, a group seeking to revise the county’s strict grading policy, and showed up at her first meeting with a campaign plan in hand. “I said, ‘You guys are never going to win this doing a PTA dog and pony show,’ ” she recalled. “ ‘You need to run this like a political referendum on the superintendent and the School Board.’ ”

That strategy helped Fairgrade succeed, and Lorenze hopes it will help upend the School Board.

Some in Fairfax hail Lorenze as a champion of parents. “She’s kept a lot of us informed about what’s really going on,” said Lauren Barton, a mother of students at Forestville Elementary in Great Falls. “I rely on her.”

Others discount Lorenze as the representative of a disgruntled minority.

“She spins issues, she spins statements, she takes things out of context and she writes them down,” said retiring board member Elizabeth T. Bradsher (Springfield), who battled Lorenze over a board decision to close Clifton Elementary School. “She’ll do anything she can to make sure these candidates win.”

Most of the candidates she is backing are connected with Fairgrade or the Fairfax Education Coalition, a group of parent and teacher organizations that has been critical of the board. Lorenze is communications director for both groups.

Lorenze is directing most of her energy to helping Epstein unseat Strauss, whom Lorenze blames for McLean’s large classes. “She consistently redistributes our resources to the rest of the county,” Lorenze said.

Strauss has supported a staffing formula that sends more teachers to — and thus lowers class sizes at — schools with high numbers of poor children and children who speak English as a second language.

The result is uneven class sizes. Some high-poverty schools along Route 1 in the Mount Vernon district have average class sizes, in the high teens and low 20s. In well-to-do McLean, averages hover in the high 20s, and classes can climb into the mid-30s.

Lorenze said she understands the philosophy but says it’s gone too far. Poor neighborhoods in Fairfax “make out like bandits” compared to the county’s affluent areas, Lorenze wrote on her blog.

Strauss said she agrees that budget cuts have made for untenably large classes. But she defended her support for the staffing formula. Public schools are obligated to ensure that all students achieve, she said, and that means more teachers for those who go to class with the least.

“If we don’t help the kids who need additional help, we are wasting the minds and the talents of many of our citizens,” she said.

Epstein, a former tax lawyer and Fairgrade co-founder, served as PTA president at the county’s Thomas Jefferson High School for Science and Technology. She has pledged to change the staffing formula. Like many of the candidates Lorenze is backing, Epstein has received endorsements from county teachers’ groups.

Lorenze said she never considered running for the School Board herself. She prefers campaigning to governing and can’t imagine collaborating with the administrators she has criticized for years.

“For me to have to work with them would drive me crazy,” she said. “I like the kingmaking. It’s more fun.”