Earlier this summer, we published a map of high school graduation rates by district across the United States. We’re now breaking it down and exploring trends in different states and regions.

Let’s zoom in to one of the hardest-to-see areas of our high school graduation rate map: those tiny Northeastern districts. Let’s start by looking at the New York tri-state area.

First, that large dark green district in the middle is, in fact, New York City, where the graduation rate was 71.4 percent. Around New York, New Jersey and Connecticut, higher-performing districts outnumber low-performers, but numerous places are still struggling. And they are often very close to places that excel.

Perhaps that’s not surprising given that this is the country’s most populous region, and income inequalities are vast here. Still, consider Yonkers City School District, the larger of the two green districts sitting atop New York City. There, the graduation rate was 66 percent. Three-quarters of students are economically disadvantaged. Just across the Hudson River, a cluster of districts in New Jersey have graduation rates at least 30 percentage points higher, all with significantly lower rates of low-income students.

Or look at Connecticut, where the income achievement gap on national tests is the largest in the country. Several districts with graduation rates above 95 percent border those with rates below 75 percent. And look at how closely that aligns to the income of a school district.

Related: What’s behind the Deep South’s low high school graduation rates?

Narrowing the gulf on test scores and graduation rates between low-income students — many of whom are in the state’s urban areas — and their more affluent peers has been a daunting obstacle in Connecticut for years. As these maps show, progress has been slow.

“The density of poverty brings a host of issues that these school districts have to deal with that aren’t necessarily shared by the suburban counterparts,” said Jeffrey Villar, the executive director of Connecticut Council for Education Reform, a nonprofit devoted to closing the achievement gap. “We need to look at structuring those districts and staffing in different ways. So much of what we do is take the suburban education model and apply it to dense [urban] areas. Then we scratch our heads and wonder why we get a result we’re not looking for.”

The tri-state area isn’t alone in its stark inequalities. Take Massachusetts for comparison.

The difference between the eastern and western parts of the state is striking. The majority of western districts graduated fewer than nine out of 10 students. Western Massachusetts had only three districts with graduation rates above 95 percent. Eastern Massachusetts had dozens.

That’s not to say that the eastern part of the state is without problems. Many districts haven’t been able to bring their graduation rates above even 80 percent. Boston, the large dark green district on the coast, had a 66 percent graduation rate. Its neighbors to the north, which are 37 to 47 percent economically disadvantaged compared to Boston’s 49 percent, only did — at best — about 11 percentage points better.

Still, the East-West comparison is noteworthy. Western Massachusetts is more sparsely populated; the eastern part of the state has more affluent households. These, and other factors, undoubtedly come into play to influence this map.

Much like disaggregating test score data by race and income in the early 2000s revealed inequities in what were generally considered to be good school systems, breaking apart graduation rates by school district shows that even high-performing states have pockets of failure. New Jersey, Massachusetts and Connecticut all report graduation rates above the national average. But only comparing at the state level masks some real problems.

Keep checking back as we examine other regions of the United States in the weeks to come. Tell us places you want to see covered in the comments or on Twitter: @sarahbutro or @hechingerreport.

[Cross-posted at The Hechinger Report]

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Sarah Butrymowicz received a bachelor's degree from Tufts University and an M.S. from the Columbia University Graduate School of Journalism.