In the 1970s, when Sam Tasby's lawsuit forced Dallas ISD to stop slow-walking desegregation, white enrollment began to drop like a stone. In 1970, there were 94,383 white students in the district. By the end of the decade, the district enrolled fewer than half that many, 42,030. The rate of decline hardly let up until 2008, when Dallas reached a nadir of 7,207 white students.

DISD began desegregation as a majority white district. In recent years, the white population has hovered below 5 percent. By the end, DISD's Anglo exodus could be rationalized as a response not to racial mixing but to concentrated poverty, flagging test scores and an inept administration perennially mired in scandal.

The white exodus didn't stop at DISD's boundaries. The inner-ring Dallas suburban school districts that boomed with the initial out-migration from DISD have experienced a similar if in most cases slightly less dramatic version of white flight.

In 1997, 138,760 white students enrolled in Dallas County school districts. Last school year, there were 61,538 white students enrolled in those same districts, according to Texas Education Agency data, with another 5,000 enrolled in charter schools.

It's not just that there are fewer school-age white children in the Dallas area. On the contrary, while their relative numbers have shrunk modestly, Census data show that there were 140,000 more school-age (i.e. ages 5-17), non-Hispanic white children in the Dallas-Fort Worth metropolitan area in 2014 than there were in 2000.

Some of Dallas County's missing white children attend private schools, but most seem to have have moved to increasingly far-flung suburbs. Collin County gained 40,000 white students between 1997 and 2015 even as Plano ISD, the white flight destination of the 1990s, lost 10,000 white students. Denton County public schools gained 20,000 students, Rockwall County 6,000. Keller ISD absorbed 8,000, Saginaw 4,000.

Teasing out causation is tricky. In an urban area as thoroughly suburbanized as Dallas, it's a natural progression for families with the means to do so to trade in an older, smaller home in an aging inner-ring suburb for a newer, larger home in a booming exurb. That the families with means are disproportionately white is a relic of a racist past. And if many of these families are indeed fleeing — and, given how heavily the perception of "good schools" factors into residential real estate, this is basically indisputable — is it race they're running from or poverty? Increasing poverty, after all, does awful things to a school and school district's academic performance and, by extension, its reputation.

But in the end, given the close link between race and socioeconomic status, whether people are fleeing poverty or race is a distinction without much difference for those kids left behind, who wind up in schools filled with other poor kids supported by an often foundering tax base. And if those families try to move for a better opportunity, the opportunity just begins to move upon their arrival.

The Southern Suburbs

The change has been most dramatic in Dallas County's southernmost school districts: Cedar Hill, DeSoto, Duncanville and Lancaster ISDs. In 1997, DeSoto and Cedar Hill were majority white, Duncanville was nearly half (48.6 percent) and Lancaster was slightly under a third (31.2 percent).

DeSoto is now 3 percent white, having lost 91 percent of its white population. The number of low-income students, meanwhile, has quadrupled:

The story is much the same in the other districts. Lancaster's white population is now 2.1 percent, down 89 percent from 1997. Its low-income population has increased by 237 percent. It's now neck-and-neck with Dallas in terms of the percentage of its students on free and reduced lunch.

Duncanville has lost 87 percent of its white population and has experienced a 204 percent increase in low-income students.

Cedar Hill's white population has dropped by 83 percent, with a 311 percent increase in its population on free-and-reduced lunch.

The Big 'Burbs - North & East

The southern school districts are all relatively small, magnifying the impact of racial and socioeconomic turnover. But Dallas County's big suburban districts — Carrollton-Farmers Branch, Garland, Grand Prairie, Irving, Mesquite, and Richardson, all of which have more than 25,000 students — saw significant declines in the white population at the same time that they experienced significant jumps in the low-income population.

Four of the six districts (Carrollton-Farmers Branch, Garland, Mesquite, and Richardson) were majority white in 1997 with fewer than a third of their students classified as low income.

Mesquite had the highest share of white students at 70.6 percent and also saw the largest decline of the four. By 2015, the number of white students had dropped by 68 percent while its low-income population had surged by 266 percent.

Carrollton-Farmers Branch lost 65 percent of its white population and saw an increase of 175 percent in low-income students:

Garland's white population dropped by 52 percent. Its low-income population increased by 160 percent.

Richardson ISD's population was the most stable. Its white population decreased by a mere 44 percent while its low-income population only jumped by 131 percent.

The Big 'Burbs - West

Dallas County's other two big suburban districts, Grand Prairie and Irving, were further along in their transition in 1997. Both the Grand Prairie and Irving school districts were nearly half low-income (45.1 percent and 49.2 percent, respectively) and less than half white (42.5 and 43.4 percent). Still, change happened rapidly.

Grand Prairie is now 12 percent white and 72 percent low income.

Irving is 9.2 percent white and 79.6 percent low income.

Dallas

As previously mentioned, white families continued to abandon DISD until a few years ago. The white population dropped 55 percent between 1997 and 2015. The low-income population has continued to inch upwards. Both, however, seem to have leveled off, with the white population actually increasing slightly — very slightly — over the past couple of years.

The Outliers

Two Dallas County school districts — Coppell and Sunnyvale — are literal outliers. The municipalities do not border the city of Dallas and developed later. In Coppell, the school district's white population peaked in 2003 and then began a steady decline while its low-income population more than doubled:

Sunnyvale by contrast, has been steadily gaining white students, though they now make up barely a majority of the student body, down from 96.1 percent in 1997. The district is 13.3 percent low income.

Highland Park is a metaphorical outlier. Like Sunnyvale, it's white population has increased. Unlike Sunnyvale, its low-income population has not. The percentage of Highland Park kids on free-and-reduced lunch remains, as it's always been, at 0.