The respected center-left, Washington, D.C., based Brookings Institution released several mostly unnoticed analyses in 2017 on the racial makeup of America's over 86,000 district and charter public schools. The analysis is accompanied by an interactive map that allows interested parties to examine the racial balance of any individual public school in the country.

While issues of race and segregation often lead to debates involving more heat than light, these reports offer a nuanced description of how integrated - or segregated - schools are.

Here are three key questions to which the report offers perceptive answers, concluding with a key practical lesson learned from taking this approach.

Is there a straightforward way to measure segregation in traditional and charter public schools?
There are, historically, five primary - though different - ways of measuring the segregation or integration of public schools, all of which offer unique insights about the current state of school segregation.

Two measures focus on the relationships between groups, typically in a binary manner - i.e., African American and white students.

• The Exposure Index measures the percentage of white (or African American) students in the average African American (or white) student's school. For example, the average African American student attends a school that is 34% white.
• The Isolation Index measures what percentage of white or African American students attend a given school, showing how clustered students from one group are with others like themselves. For example, the average white student attends a school that is 79% white, though, on average, the district where the school is located is 63% white.

Is there a straightforward way to measure segregation in traditional and charter public schools?

There are, historically, five primary - though different - ways of measuring the segregation or integration of public schools, all of which offer unique insights about the current state of school segregation.

Two measures focus on the relationships between groups, typically in a binary manner - i.e., African American and white students.

• The Exposure Index measures the percentage of white (or African American) students in the average African American (or white) student's school. For example, the average African American student attends a school that is 34% white.
• The Isolation Index measures what percentage of white or African American students attend a given school, showing how clustered students from one group are with others like themselves. For example, the average white student attends a school that is 79% white, though, on average, the district where the school is located is 63% white.

All five of these approaches are flawed as a tool to help education and community leaders identify schools that are more racially imbalanced than is to be expected given the geographical catchment areas from which they draw students. On the other hand, they do provide useful information that gives education and community leaders an insight into a particular aspect of the racial imbalance issue, and for that reason should continue to be used.

The analysis by Brookings is important because it offers a new way of calculating racial imbalance by comparing the racial composition of each public school in the country to that of the school age population within a fixed radius from that school. Thus, a school that has an enrollment that is 65% black when its surrounding neighborhoods are 45% black looks very different in the Brookings index of racial imbalance than a school with the same proportion of black students but with surrounding neighborhoods that are also 65% black. The former school is racially imbalanced, whereas the latter is not.

How has racial segregation changed over time?

During the 1960s, African American and white racial integration across public schools within school districts increased, though by the late 1980s schools were slightly more segregated, partly due to so called "white flight" to the suburbs.

One interpretation of this trend is that schools have "re-segregated." But using information from several of the indices described above allows for a more nuanced - and accurate - understanding.

What some call "re-segregation" is the fall in the proportion of majority white schools from 81% in 1988 to 58% in 2013, creating far fewer white majority schools for African Americans to attend. But this is due primarily to the influx of Hispanic students, exposing African American and white students to more Hispanic students. So while African American and white students are less likely to share classrooms with each other today than they were 20 years ago, this is largely a mechanical result of the influx of Hispanic students.

Are charter schools more racially imbalanced than traditional district schools?

The Brookings analysis shows that charters are now serving almost equal percentages of white, African American and Hispanic students. But this result represents the averages across all charter schools rather than the degree of racial balance for individual charter schools.

In other words, if there were only three charter schools in America, each serving exclusively one racial group, the national average would show charter schools serving equal percentages of white, black and Hispanic students.

When individual schools are compared against their geographical catchment zones using the Brookings approach, or when the movement of individual students from traditional to charter public schools is tracked, there is evidence that charters, on average, are more racially imbalanced than traditional district schools.

In particular:

• Longitudinal studies tracking the flow of students from traditional district schools into charters indicate that students typically move into a more segregated charter school than the district school they leave. This results mostly from African American students moving to charter schools located chiefly in urban centers ¬- though this varies by state. For example, in California, non-African American charter students enter schools slightly more diverse than the district schools they left.
• Area studies, using the Brookings approach, find that charter schools are on average 6 % more black, 2% less white and 3% less Hispanic than their neighborhoods.

The reasons for charter schools being more racially imbalanced than traditional public schools are complicated. But there are answers. For example:

• Charters are schools of choice and - unlike district schools that often restrict enrollment to neighborhood boundaries - can enroll students from any neighborhood.
• Policymakers creating charter laws may intentionally name urban minority students in underperforming district schools as priority students for charter enrollment.
• Charter school organizers may single out low-income, urban, minority families with fewer quality schools to attend as those they choose to serve.

What is the main lesson learned from this discussion?
The Brookings analysis cautions us against a too simplistic approach to the racial composition of charter schools: There are two simple stories that can be told about charter schools and racial segregation. One is that charters will deepen segregation, in part by allowing for African American and white parents to choose schools in which students of their race dominate enrollment. Another is that charters will lessen segregation by loosening the connection between neighborhood and school. Our research suggests that there is some truth to each of these stories, differing across place and time but when taken alone, each is too simplistic.

In short, there are many goals that charter schools can achieve, with tension or even conflict between them. Be clear - not simplistic - about tradeoffs between goals when examining the racial makeup of charter schools.