Fig. 2
From: Equal opportunities for all? Analyzing within-country variation in school effectiveness
Schematic illustration of between-school variation in student selection and added-year effects. Figure displays the results of the regression (dashed lines) of achievement scores (y-axis) on age in months (x-axis) and an added year of schooling in a sample of students from two adjacent grades at three schools (A, B, and C). The between-school variation in the intercepts reflects differences in student selection. The between-school variation in the added-year effects (regression discontinuities) reflects unequal school effectiveness