Despite widespread use of effect sizes across industries as a standardized measure of impact, effect size calculations remain one of the most incorrectly applied and misinterpreted statistics. An effect size is nothing more than a standardized comparison, or “effect” , that captures the difference between an average value and a meaningful comparison in the metric of standard deviation.
The single most important pitfall for Illinois schools to avoid when interpreting ISBE Student Growth Percentiles (SGPs)
The Illinois State Board of Education (ISBE) recently released student growth percentiles (SGPs) to Illinois school districts in preparation of the new school accountability system and the launch of the new Illinois school report card. While incorporating student growth into the school accountability system is a step in the right direction, it is important to recognize that ISBE SGP results are reported within an accountability context not a school improvement context.
Based on recent information provided by the Accountability Technical Advisory Committee’s (TAC) recommendations to ISBE, it is likely that ISBE will move away from linear regression toward Student Growth Percentiles (SGPs) as a means to measure student growth under the new school improvement and accountability system.
The fundamental purpose of setting school improvement goals is to assess the effectiveness of improvement efforts. The utility of the school improvement process rests on the inferences one can draw from meeting a goal. For example, a typical school improvement goal may be “increase the percentage of students meeting standards in grade 4 reading by 5%.” While this type of goal is specific and concise, the results will provide little to no information as to the effectiveness of improvement efforts. Why? Because increasing grade 4 reading by 5% is likely an arbitrary goal that is unrelated to school performance and not evidence-based.