Third-grade scores are probably strongly influenced by poverty and home life, while growth from third to eighth grade is probably more influenced by the quality of schooling.

Growth rates better isolate the contribution to learning due to experiences during the schooling years. Grade 3 average scores are likely much more strongly influenced by early childhood experiences than the growth rates. Some caution is warranted in interpreting the average growth rates as pure measures of school effectiveness. Nonetheless, relative to average test scores, the growth rates are closer to a measure of school effectiveness.

If we take the growth rates as rough measures of school effectiveness, then neither socioeconomic conditions nor average test scores are very informative about school district effectiveness. Many districts with high average test scores have low growth rates, and vice versa. And many low-income districts have above-average growth rates.

The findings also suggest that we could learn a great deal about reducing educational inequality from the low-SES communities with high growth rates. They provide, at a minimum, an existence proof of the possibility that even schools in high-poverty communities can be effective. Now the challenge is to learn what conditions make that possible and how we can foster the same conditions everywhere.

Read the full article on low-income school districts by Kevin Drum at Mother Jones