The rapid gentrification of many large American cities represents a triumph and an opportunity for Republicans—a triumph because it was mainly Republican ideas (welfare reform, aggressive crime-fighting tactics, pro-growth policies) that set the trend in motion, and an opportunity because the wealthier, and frankly whiter, new residents are more likely to vote for the GOP.

Yet a natural Republican constituency—parents with children—continue to leave cities once their kids reach school age.  This is bad for Republicans, to be sure, but it’s also bad for cities, as much capital—human, social, and financial—decamps for the suburbs.

So why are 20-something single city-dwellers turning into 30- and 40-something suburban moms and dads? It’s education, stupid: a paucity of high-quality public schools.

Some hope that current education reform efforts—raising standards, holding teachers accountability, creating more charter schools—could help persuade these parents to keep the faith with big cities. And they might, at the margins. But most of these efforts don’t address the fundamental challenge urban schools face: The diversity of their student population.

Let me be clear: I don’t mean racial or ethnic diversity, which is a huge plus for everybody—the students, the parents, and society at large. Nor is it exactly socio-economic diversity. The big challenge is academic diversity: Students are coming into school with vastly different levels of academic preparation. Finding a way to make sure that everyone gets what they need—including affluent children, who will tend to come in far ahead of their peers—is no easy trick. If you’re a Kindergarten teacher, and some of your students are already reading Harry Potter, while others don’t even know their letters, how on Earth do you handle that?

Yet the typical liberal response to perplexed professional parents who worry about whether their children will be challenged is: tough luck. They sneer at “gifted and talented” programs, which they view as inherently elitist and inequitable; they deplore “selective admissions” schools like Stuyvesant; and they pore over charter school data for any signs of “skimming” the best and brightest.

The left’s leveling impulses, then, practically beg parents of means to choose private schools or pack their bags for the burbs. But this approach is also problematic for the poor—in particular “striving” families and their children who want to defy the odds and use academic excellence as a springboard to the middle class. Note the derision shown to the Success Academies, for instance—a non-profit network of charter schools that’s getting remarkable results with a mostly low-income student population. Rather than applaud Eva Moskowitz’s plans to expand to 100 schools citywide, they work at every turn to slow her down.

The urban left’s brand of “equity” is a perverse one. It focuses on equality of outcomes rather than equality of opportunity. It rejects the notion that fairness demands every child to be challenged, to learn something new each day, to fulfill his or her own potential. And it pretends that pushing ambitious students to the suburbs is somehow a more equitable outcome than providing city schools that serve their needs.

All of this offers an opening for the right, and for Republicans, who should become the Party of Strivers, as David Brooks argues. Brooks wrote in another column that we should figure out “what exactly does it take these days to rise? What exactly happens to the ambitious kid in Akron at each stage of life in this new economy? What are the best ways to rouse ambition and open fields of opportunity?”

Here’s what: Republicans, and urban Republicans in particular,  should call for the expansion of gifted and talented programs while maintaining tough, but fair, entrance requirements; charter schools that embrace a college-prep, high-expectations culture; selective-admissions magnet schools that allow our most academically prepared students to push one another; and merit-based scholarships at flagship public universities.

Parents of high-achieving students—whether they be rich or poor, newcomers or old-timers—deserve schools that will challenge their children. If they don’t find them in the city, they will move. It’s up to Republicans to offer another alternative.

-Mike Petrilli

This article first appeared on Public Sector Inc.