Rarely, if ever, has the nationally acclaimed Fairfax school system looked ahead to such a turbulent change in leadership. At least half of its 12 school board members will step down Dec. 31. Its superintendent, Jack Dale, will depart in 2013.

And now, a grass-roots revolt by an unlikely coalition of parent activists and overworked teachers looks likely to push the system in new directions in the Nov. 8 school board elections.

The consequences could be long-lasting. There’s an excellent chance that a large minority or even a majority of the new board — which will pick and oversee Dale’s successor — will have won after campaigning strongly against the status quo.

“We need a new norm in the Fairfax county school board,” Lolita Mancheno-Smoak, a business consultant seeking an at-large seat, said at a debate in the Great Falls Grange hall Tuesday. She called for policies “to benefit the child in the classroom first, not the bureaucracy.”

I generally sympathize with popular uprisings, and there’s no mistaking that this one is genuine. It will be a plus for the county if it succeeds in one of its main goals: forcing the school administration to be less arrogant and more responsive on issues such as discipline, grades and school hours.

“Right now, the most important thing facing this school system is restoring a stronger partnership with teachers and parents,” Megan McLaughlin, a leading parent advocate who is running to represent the Braddock district, said in an interview. Dale “has ignored authentic parent concerns that are data-driven,” she said.

But voters need to be cautious, because some of the insurgents seem mainly to want Fairfax to spend more of its budget on schools in its most affluent, least diverse neighborhoods.

That’s the not-so-hidden agenda behind calls in the campaign to reduce class size in schools with the highest student-teacher ratios. Such a goal, though desirable in theory, risks weakening the county’s commitment to devoting extra resources to low-income schools and those with many foreign-language speakers.

Defenders of the current administration, such as board Chairman Jane Strauss (Dranesville), say it’s risky to meddle with policies that have made Fairfax one of the country’s highest-achieving large districts.

The upheaval could increase Republican political influence in Fairfax, because most of the reformers (although not all) are aligned with the GOP. School board elections are technically nonpartisan, but the parties endorse slates of candidates.

The possibility that the new school board would turn too conservative has prompted Sharon Bulova, Democratic chair of the Board of Supervisors, and some of her colleagues to plan an unusual mailing this week clarifying whom the party is endorsing.

“I am very concerned about voters being confused about who’s running for school board and what they stand for,” Bulova said. She said it was the first time that Fairfax Democrats have sent such a mailing in a school board election.

The rebellion springs from three overlapping movements of popular discontent.

One was a series of parent protests against rigid discipline practices, tough high school grading policies and early high school opening hours. Advocates got steadily more frustrated as they felt that both the Dale administration and the school board dismissed their concerns.

“The community gets no input. We sit and listen,” said Jody Bennett of Vienna, an activist at the Great Falls event. She wore buttons supporting insurgents Steve Stuban, seeking an at-large seat, and Louise Epstein, who is challenging Strauss in the Dranesville district.

Another source of discontent was a backlash in well-to-do communities over swelling class sizes and school closings or boundary changes that shifted students to more economically and racially diverse schools.

Finally, teachers have grown increasingly dissatisfied over rising workloads. That explains why the dissidents have received support from both Fairfax teachers associations, one of which is usually aligned with the Democrats and the other with Republicans.

Teachers complain that the school system has piled on too much work as they’re pressed to raise students’ scores on standardized tests. They’re concerned about extra time they’re required to spend on a new Web-based tool called eCART, designed to help them prepare students for exams.

“You take a lot of time working with technology, and it takes you away from interacting with children,” said Fairfax Education Association President Michael Hairston, whose group represents nearly 6,000 educators.

Some of the insurgents say they can get more money to reduce class size in well-off communities by cutting back on use of eCART. Others say they will find money by using tough audits to eliminate central office waste.

Either approach could be fine. Just don’t do it by penalizing schools that need help most.