Last month, a smart young writer at the Washington Post named Lydia DePillis wrote a provocative article about cities and families that lit up every urbanists' social-media feed. In it, she observed something parents have known for a long time: Kids are expensive. "Why, from a purely economic standpoint, would a city on the make try to attract families at all?" she asked.

The question stopped me in my tracks. For America's comeback cities, the ability to land and keep middle-class families is considered a badge of success. Over the last decade, Philadelphia has definitely become a city "on the make." It has proudly drawn thousands of new residents of childbearing age - that millennial generation - and showered them with the amenities they love, from bike lanes to beer gardens to spray parks, in the hope they'll stay and raise families here.

The irony, of course, is that this week the city's grossly underfunded schools just barely managed to open on schedule. Basic educational amenities that suburban districts take for granted, such as guidance counselors and nurses, are a luxury. Even if the legislature approves Philadelphia's $2-a-pack tax on cigarettes, it may not be enough to get the district through the year, never mind next year or the year after.

Philadelphia has undergone such a quick and heady transformation, as housing construction exploded and the streets filled again with people, that it hasn't spent much time asking itself, what next? Can this recovery be sustained once millennial parents start confronting the first day of kindergarten in a classroom with 35 kids and no teacher's aide?

DePillis' essay startled because it suggested the parenthood-and-cities thing isn't all it's cracked up to be.

To be clear, she isn't advocating that cities actively discourage families. She simply reminds us that providing for children diverts resources that could instead be spent to make cities more attractive to lower-cost folks, i.e., affluent professionals. Citing a 2001 study, she notes that a traditional two-parent, two-child household cost Washington $6,200 a year in services, while a childless couple generated a net gain of $13,000.

When I mentioned her piece to a couple of planners and educators, I got the kind of response that must have greeted Jonathan Swift's Modest Proposal. I might as well have suggested that Philadelphia kids be served up as a haute dish during Restaurant Week.

But, when you think about it, isn't Philadelphia effectively embracing the exact antifamily policy that DePillis describes?

We dole out 10-year property tax abatements to encourage new housing construction, even as the program drains the schools of revenue. Who do we expect to live in those houses, which are now typically built with three bedrooms? We say we want young, dynamic, "knowledge workers" who will establish deep neighborhood connections and improve the city overall, and then we sabotage the thing they care about most - their children's knowledge. Less mobile working-class families, meanwhile, are simply left to fend for themselves.

Who's to blame for the schools' starvation diet? Most education advocates fault Harrisburg in general and the Corbett administration in particular. It does seem incredible that the state took over the deficit-plagued Philadelphia district in 2001 promising to show us how it's done, only to sink the schools even further into bankruptcy in the span of a decade. The state's contribution to the district's budget has remained flat, and the district has been forced to drastically slash its spending.

The worst part is that Philadelphia can't control its destiny. Unlike other Pennsylvania municipalities, city residents don't elect a school board. While the mayor appoints two of the five members of the School Reform Commission, that doesn't give him (or, someday, her) the ability to coordinate education policy with the other important goals, like growing the population, creating an educated workforce, reducing inequality, and improving the city's physical condition.

Meanwhile, our competitor cities - New York, Washington, Chicago - are investing smartly in education. Yes, that's the more expensive option, but they understand that the added costs are crucial to their long-term success. For instance, both New York and Washington made a decision to offer to 4-year-olds universal free pre-K because they want to grow their own knowledge workers, rather than keep importing them from the suburbs. Alan Ehrenhalt, editor of Governing Magazine, told me that Philadelphia's schools crisis may be the most "extreme case" he has seen.

Would this municipal shortsightedness be happening if Philadelphia had a bigger constituency to lobby for good schools? Since 2000, the under-18 population has shrunk from 25 percent to 22 percent. Yes, this follows the national trend: the percentage of households with children dropped from 50 percent in 1960 to 30 percent today. That makes it even harder to prevent DePillis' scenario from playing out here.

Policies that discourage families would be ruinous, argues John D. Landis, chairman of the University of Pennsylvania's regional planning department. "If your goal is to purge cities of children in the name of fiscal solvency, (then) head down to Sun City, Ariz., whose fiscal solvency is exceeded only by its boringness."

No argument there. My ideal city is a diverse, multigenerational one, with children, seniors, and everyone in between. My husband and I raised our daughter in the city, subjecting her to 12 years of public school. I'd do it all over, even now.

In theory, Philadelphia can just keep replacing the cohort of 25- to 35-year-olds if families bolt. But how successful can a transient city be? Philadelphia has prospered because it offers an authentic and diverse neighborhood life. Where else could the Taney Dragons emerge?

Give up on the schools, and the whole house of cards could collapse. From a purely economic standpoint, the schools crisis isn't just about kids. It's about all of us.


Note: This column has been updated to reflect the correct amount of the state's contribution to the school district's budget.