Figure 1 shows our estimates of the average impact of attending a charter school on test scores, expressed in standard deviation units. (educationnext.org)
The impacts are presented as effect sizes (which represent the differences between groups in standard deviation units) for eight measured outcomes across the domains of literacy, language, and math. (educationnext.org)
The vertical axis measures the effect of California Math relative to the composite alternative in student standard deviation units. (educationnext.org)