Boston emerged as ground zero in the recent charter school debate on Beacon Hill. Not only was state Sen. Sonia Chang-Diaz of Jamaica Plain, co-chair of the Legislature’s education committee, the key player in the Senate showdown over the issue, but Boston district public school parents emerged as a strong voice in opposition to any expansion of charter schools in the state.

That made for an interesting context for the latest round in the never-ending battle over charter schools, publicly funded schools that operate independent of school districts and enjoy more leeway over staffing, budgeting, and the structure of the school day.

In March, the Globe reported that some 2,200 parents had signed the petition of Quality Education for Every Student, a Boston parent group that formed to fight charter expansion, which critics say diverts needed funding away from district schools.

Their side carried the day as the Senate killed any efforts for this year to expand the number of charter schools allowed in low-performing Massachusetts districts. But the issue will surely return. The State House News Service reported this week that charter backers are now eyeing a possible 2016 ballot campaign to raise the limit on charter schools.

Most urban-dwelling parents would jump at chance to send their child to a high-performing school with high standards for academic achievement, low tolerance for disruptive behavior, and where students have a track record of heading off to good colleges and succeeding there. So no one can blame the large number of Boston parents involved in the anti-charter effort who have, in fact, done that by sending their children to one of the district system’s elite exam schools.

Roxbury Prep has among the highest MCAS scores in the state, with 93 percent of
8th graders scoring proficient or higher in English, 89 percent doing so in math.

But that does raise the question of whether these parents are, in effect, pulling up the drawbridge on low-income minority families, who dominate many charter-school waiting lists and who are also eager to have viable education options besides the city’s standard district schools. The same question might be asked about voters — and legislators — in more affluent suburbs who oppose more charters.

Choice lies at the heart of this debate, and the question, at some level, comes down to whether those who have plenty of it will extend the same privilege to those who typically have very little.

A seat at Boston Latin School and the Boston system’s two other 7-12 grade exam schools, which grant admission based on a performance on a standardized test, is regarded as the answer to many Boston families’ prayers — and it’s the thing that keeps many middle-class families from fleeing to the suburbs.

Students at the exam schools score at or near the top of all schools statewide on the MCAS exam, and many go on to top colleges and universities. When it comes to “serving all students,” however, the refrain frequently sounded by charter opponents, who accuse the autonomously run schools of “creaming” good students off the top of the pile, the exam schools don’t score as well. While 30 percent of Boston district students are English language learners, at Boston Latin that figure is an astonishing 0.1 percent. Special ed? For Boston overall, it’s 19.5 percent. At Latin it is just 1.1 percent.

The effect of past court decisions, which threw out set-asides that allowed schools like Latin to ensure representation of minorities, has made its admission exam more of a screening test that effectively rewards middle-class families. The percentage of low-income students in the district overall (78 percent) is more than double what it is at Latin (33 percent). In terms of race breakdown, blacks and Latinos make up just 20 percent of the Latin School population, while they account for 75 percent of the entire district population.

At Roxbury Preparatory Charter School, by contrast, a grade 5-8 school in Boston’s Mission Hill neighborhood, 11 percent of students are English-language learners, 13 percent are special needs students, 96 percent are black or Hispanic, and 78 percent are from low-income households. Roxbury Prep students, who arrive one to two grade-levels behind in English and math, have recorded among the highest MCAS scores in the state, with 93 percent of its eighth-graders scoring proficient or higher on the English portion of the test and 89 percent scoring proficient or higher in math.

Thousands of families remain on waiting lists for seats at high-performing charter schools like Roxbury Prep. These families are seeking out the best education possible for their children, just as so many Boston families are when they have their sons and daughters compete for seats at the city’s exam schools. For all sorts of reasons, black, Hispanic, and poor children enter sixth grade — the point at which students must take the exam school admission test — with much tougher odds of scoring well enough to win a seat at these schools than children from middle-class homes.

Those charter schools offering a rigorous college-preparatory curriculum, therefore, represent something of an exam school for these students, a place for strivers who may not yet have had the same opportunities as other children to blossom, but whose families desperately want the same chance for them to aim high and receive an education that will prepare them for college.

Not only do Boston’s exam schools offer many better-off families an alternative to the city’s low-performing district high schools, those families also have the most time-honored American school-choice option of all: moving to a different community.

Many middle-class Boston parents would have been on a fast-track to the suburbs or to a costly private school had their child not been accepted to an exam school. Many contemplate such school choices even earlier. A few months ago, the Globe reported on the annual release of elementary school assignments for the coming school year. The paper caught up with a Jamaica Plain mother who, hedging her bets against getting assigned to an undesirable school in the complicated lottery system, said she had spent the previous weekend house hunting with her husband in Wayland.

But a move to Wayland or shelling out private school tuition payments are not options for lots of families in Boston or in other Massachusetts communities with struggling district schools that can’t always deliver the education parents want for their children.

The dirty secret of American public education is that children have vastly different schooling options depending on their family’s income. That’s because housing costs are so closely tied to the quality of a school district. In 2011, the Thomas B. Fordham Institute, a Washington-based education think tank, issued a report on what it dubbed “America’s Private Public Schools.” The report spotlighted public schools that serve virtually no low-income children. More closely resembling the demographics of private schools, these are suburban schools “whose doors are effectively closed to poor children,” says the report, “while proudly waving the ‘public school’ flag.” The report included breakdowns by metropolitan regions, including Boston.

Elizabeth Warren’s 2003 book called for a regional voucher system – she called it a
needed “shock to the educational system” — that would break the link between
housing costs and school quality.

A decade ago, a rising star at Harvard Law School raised these same issues in writing about the financial straits of over-extended middle-class families desperate to buy their way into a decent school district. “It is time to sound the alarm that the crisis in education is not only a crisis of reading and arithmetic; it’s also a crisis in middle class family economics,” wrote Elizabeth Warren in her 2003 book The Two-Income Trap. “At the core of the problem is the time-honored rule that where-you-live dictates where you go to school,” she wrote. “Any policy that loosens the ironclad relationship between location-location-location and school-school-school would eliminate the need for parents to pay an inflated price for a home just because it happens to lie within the boundaries of a desirable school district.”

Warren then puts forward a radical solution that might shock liberal followers who are unfamiliar with her take on this issue. “A taxpayer-funded voucher that paid the entire cost of educating a child (not just a partial subsidy) would open a range of opportunities to children from all income levels,” wrote Warren, who also shared her thoughts on the issue in this 2003 Conversation interview with CommmonWealth.

A voucher system across a metropolitan area, with open-enrollment across municipal lines, would break down the wealth barrier that creates the “private public schools” the Fordham Institute report highlighted. Indeed, writing almost a decade before the Fordham report came out, Warren cast the issue in very much the same terms. “Schools in middle-class neighborhoods may be labeled ‘public,’” she wrote, “but parents have paid for tuition by purchasing a $175,000 home within a carefully selected school district. (Her price reference, of course, is in 2003 dollars and isn’t pegged to Boston and other high-cost regions.)

Warren acknowledges that an “all-voucher or all-school choice system would be a shock to the educational system,” but says “the shakeout might be just what the system needs.”

No one is contemplating that sort of shock to the system, and Warren has gone quiet on the issue since jumping into politics and becoming the darling of a resurgent American liberalism with lots of teacher union support. But the underlying principle she articulated remains a powerful argument for a decidedly progressive idea — that more school choices for families of all means represents a leveling of the playing field that ought to be embraced by all who believe in the ideal of public education as society’s great equalizer.