Research shows that integration benefits all students. But the experience of Howard County...demonstrates that bringing students of different backgrounds together in the same schools isn't enough to ensure their success. Where educators have long spoken of the achievement gap — the differences in academic performance between white students and black, and affluent and poor — some are now focusing on the so-called opportunity gap.

To get to their new school, Tilton Elementary, the children from Marconi had to cross different gang lines and new drug turfs, parents at Marconi complained. There were new teachers, new students and, in some cases, a longer walk. And the neighborhood itself was losing one more bit of precious ballast: the rare public institution that held them together ... Based on the city’s own criteria, Tilton barely rated a “good standing” designation, and so was only marginally better than Marconi.

Once the most densely populated part of the city, it was by the 1990s riddled with abandoned buildings and vacant lots. And it contained an extraordinary amount of public housing. While some of that housing was built before World War II as segregated housing for blacks...most was constructed after the United States Supreme Court struck down racially restrictive covenants. Yet it conformed to traditional patterns of segregation.

In Southern states...county lines often double as school district lines, creating "less opportunity for intentional segregation." Instead, the researchers found the greatest disparity tended to occur in the country’s manufacturing centers: Michigan, Wisconsin, Indiana, Illinois, Ohio, and Pennsylvania. In the study, the term "segregation" is referring to class separation, not race. The two often overlap, however, creating what some allege is a legal way to essentially continue racial segregation

In public, most women wear baggy black gowns...to hide their forms, as well as veils that cover their hair and faces, with only thin slits for their eyes ... Many Saudis mix in private, and men and women can usually meet in hotel lobbies with little problem. Others do not want to mix and see gender segregation as part of their cultural identity. In some conservative circles, men go their whole lives without seeing the faces of women other than their immediate family — even their brothers’ wives.

Housing discrimination was legal until 1968. Even if black Americans managed to secure home loans, many homes were off-limits, either because they had provisions in their deeds prohibiting their sale to black buyers or because entire communities — including publicly subsidized middle-class developments like Levittown on Long Island and Stuyvesant Town in Manhattan — barred black home buyers outright.

Though Arabs represent 20 percent of Israel’s population of 8 million, Jews and Arabs rarely interact. According to government data, 90 percent of Arab-Israelis live in all-Arab communities ... In a country with a segregated education system, Arab and Jewish children learn in separate schools, and just 10 percent of Jews speak fluent Arabic. It’s mandatory for Arab students to learn Hebrew, but not the other way around.

A new analysis of reading and math test score data from across the country confirms just how much socioeconomic conditions matter. Children in the school districts with the highest concentrations of poverty score an average of more than four grade levels below children in the richest districts ... the largest gaps between white children and their minority classmates emerge in some of the wealthiest communities, such as Berkeley, Calif.; Chapel Hill, N.C.; and Evanston, Ill.

"White flight" is usually described as a post-World War II phenomenon, one that required highways and suburbs and big lawns to flee to. But whites in northern cities really began re-sorting themselves — specifically away from blacks — in the first decades of the 20th century, and what happened then remains relevant to American cities...still racially divided today ... The suburbs effectively didn't exist at the time, so whites were leaving these neighborhoods for other neighborhoods in the city.

In a neighborhood derided as “Crackwood” just a few years ago, demand is so strong that one in three Kirkwood properties sold for asking price or more in the third quarter of 2015. Compare that with the late 1990s, when urban pioneers could snatch a Kirkwood house for $61,500. By late 2012, the average sale price had climbed to $173,000; today it’s twice that.