Fairfax County voters preserved at least some continuity on the School Board on Tuesday, as several incumbents defeated challengers who had demanded change in the region’s largest school system.

Half of the board’s 12 members are retiring, ensuring substantial turnover. Four of the other six were in contested races, raising the possibility that voters could elect an almost entirely new panel to oversee the county’s high-performing schools. But incumbents held their ground.

One of the board’s most crucial tasks will be choosing a successor to Superintendent Jack D. Dale. Leader of the 175,000-student system since 2004, Dale announced in September that he will step down when his contract ends in June 2013.

With nearly all votes counted, unofficial returns showed board Chairman Jane K. Strauss narrowly beat Louise Epstein in the Dranesville district. Member Kathy Smith (Sully) defeated Sheila Ratnam, and member Daniel G. Storck (Mount Vernon) dispatched Michele Nellenbach.

Incumbent Ilryong Moon was the top vote-getter among seven candidates vying for three at-large seats. The other apparent winners were Ryan McElveen and Ted Velkoff. Behind them were Sheree Brown-Kaplan, Lolita Mancheno-Smoak, Lin-Dai Kendall and Steve Stuban.

Stuban, whose teenage son committed suicide in January in an episode that prompted scrutiny of school discipline policies, trailed far behind the others.

Elsewhere, newcomers competed for three open seats: Pat Hynes beat Nancy Linton in Hunter Mill; Elizabeth Schultz easily defeated John Wittman in Springfield; and Megan McLaughlin cruised past Nell Hurley in Braddock. Newcomer Tamara Derenak Kaufax (Lee), who was unopposed, claimed a fourth open seat.

Board members Sandy Evans (Mason) and Patty Reed (Providence) were reelected to four-year terms without opposition.

Republicans and Democrats endorsed slates of contenders in the technically nonpartisan election. Heading into the vote, Democrat-endorsed incumbents held nine seats. Republicans had hoped to make substantial inroads. But the outcome suggested that Democrats gained influence, with candidates endorsed by their party appearing to hold 10 seats on the new board.

Still, the campaign was less a showdown between parties than between candidates who defended the system and those who said it needs a major overhaul.

Trust between the community and school leaders has frayed in recent years as the board waded into high-profile battles over school boundary changes, high school start times, and grading and discipline policies.

Evans said activists succeeded in spreading a message that reform is needed.

“I think we’ve changed the conversation,” said Evans, who counts herself among the activists because she had sought later high school start times before joining the board. “That’s going to be important for the next four years with the new school board.”

The discipline code has remained a key issue, she said, and candidates have widely agreed that the next board must improve its communication and relationships with parents, teachers and students.

In addition, nearly every candidate supported some ideas from activists such as hiring an ombudsman to field community concerns and an independent auditor of programs and expenditures.

Despite low turnout, the election seemed to energize some pockets of Fairfax — particularly Dranesville, where Democrat-endorsed Strauss emerged victorious from a tough fight against Epstein, a GOP-backed activist.

“The one thing that drew me here was the School Board race,” said Regina Devlin of McLean, a mother of three Fairfax graduates who said she voted for Strauss.

“We need her, because there’s a big turnover on the School Board and without her I’m worried about what might happen,” Devlin said.

Epstein drew support from some Democrats who are frustrated with the school system. One was Wati Alvarez-Correa, 56, who said she had become so dissatisfied with public education in Fairfax that she put her children in private schools.

Large class sizes in McLean were a big part of the problem, said Alvarez-Correa, who supports Epstein’s plan to bring more teachers into Fairfax’s affluent neighborhoods. That has become an issue because staffing formulas send more help to schools with greater needs.

“I don’t feel [Epstein is] going to hurt the other districts. I think she’s just going to cut waste,” Alvarez-Correa said.

Also on the ballot in Fairfax was a $252 million bond referendum for school renovation and construction. Voters overwhelmingly approved the measure.

Voters also chose school boards in Prince William and Loudoun counties. In Arlington, School Board member Abigail J. Raphael was unopposed for reelection.