Residual: The difference between the observed and the predicted score. A negative residual indicates that a school did worse than expected, while a positive residual indicates that a school scored higher than was expected.
Significance: A statistical term indicating whether the residual was statistically significantly different than expected. A certain amount of leeway is necessary, between which we say the difference is not significantly different than zero. NS means Not significant. The number of stars corresponds to the degree of significance, four stars being the most highly significant. Blue stars mean a school scored higher, and red stars lower, than predicted.
Using the residuals, we can rank the schools according to how they performed (best to worst), with the effect of poverty removed.
2. Grant Wood