- Studies find average effect size of -0.18, indicates that increasing the share of students from an ethnic minority by 10 percentage points is associated with a decrease in individual student’s test scores by 0.018 standard deviation.
- Increasing the Afro American or indigenous students share by 10 percentage points is associated with a decrease in test scores of students from those same minorities by about 0.027 standard deviation.
- Correcting for average SES affects the size of the ethnicity compositional effect to a much lesser extent
- Effects from Afro American and indigenous students seem equal to each other and appear larger than effects of immigrants.
- Compositional effects on test scores in the existing literature are generally not very large but that there is some important variation.
- Effects related to the share of African Americans (and to share of indigenous students) seems considerably stronger that effects related to share of immigrants.
- Increasing the ethnic minority share seems to have a stronger effect on students from that same ethnic minorty group than on students belonging to the ethnic majority or on other minority groups.