What neighborhood income does — and doesn't — tell you

Attendance-area wealth tracks closely with test scores. Here's how to read that without falling into the obvious traps.

Across Montgomery County, a school’s average test scores line up strikingly well with the income of its attendance area. On our analysis page you can see the relationship plotted school by school — the trend is hard to miss. But a strong line on a chart invites a few mistakes, so let’s name them.

Correlation is not causation

Neighborhood income predicting scores does not mean income causes learning. Wealthier areas correlate with dozens of things — tutoring, stability, health care, school funding history — and the test score reflects all of them at once. The chart shows an association, full stop.

”Neighborhood” is the attendance area, not the students

This is the subtle one. The income figure describes the Census block groups inside a school’s attendance boundary — not the families of the children actually enrolled. For a neighborhood school those are close. For a magnet or choice program, students may come from all over the county, and the boundary income can be wildly off as a description of who’s in the building.

Beating the line is the interesting part

The most useful thing the chart shows isn’t the trend — it’s the schools sitting above it, outperforming what their neighborhood income would predict. Those are the schools worth asking questions about. We surface them in a “beating expectations” list for exactly that reason.