Two weeks ago, former Gotham Gazette editor-in-chief and Insideschools contributor, Gail Robinson, published an article raising a familiar question: Are high-achieving charter schools pushing out underperformers to keep their test scores up? Ms. Robinson's article focused specifically on Harlem Success Academy 1, the first school opened in Eva Moskowitz´s popular charter network on W. 118th Street in Harlem.
Ms. Robinson cited state report card data indicating that the 2011 fifth grade's class size fell 36 percent in the five years students attended the school. She went on to say that this "attrition" increased in higher grades, raising questions about whether the school "counseled out" underachievers as statewide testing began in third grade.
It is important here to clarify the difference between "attrition" and change in class size, a distinction which Ms. Robinson's article blurs. As I understand it, attrition in the context of a school reflects the number of students who attended the school one year and did not return to the school the following year. Changes in class size, which Ms. Robinson frequently equates to attrition, may be either positive or negative, reflecting the net impact of students both coming and leaving.
Nevertheless, Ms. Robinson's article got me interested in finding answers to two questions. First, what is the atrition rate at Harlem Success Academy 1, and second, how does it compare to that of other schools?
The state does not release attrition data for schools, however, one can calculate attrition rates for each school relying on the two data points Ms. Robinson cited in her article: change in class size and the school stability rate.
The school stability rate is the percentage of current-year students who also attended the school in the prior year. It is not released for all grades; instead, the state only reports the figure for the highest grade taught at each school.
Using both data points, I calculated the attrition rates for Harlem Success Academy 1 and its 40 peer schools, as identified by the New York City Department of Education. Since data was not available for all grades, my analysis is limited to the oldest grade at each school. The four-year average attrition is presented in the attached chart and the complete data is available here.
Over the past four years, among peer charter schools, attrition ranged from 5 percent to 25 percent. At peer traditional public schools, attrition ranged from 8 percent to 20 percent. Harlem Success Academy 1's attrition rate was 12.73 percent, slightly less than the peer average of 13.65 percent.
Twenty-one schools had higher attrition than Harlem Success Academy 1 and 19 schools had lower attrition.
While this analysis can not answer the qualitative question of what caused some students to leave Harelm Success Academy 1 over the past five years, it does indicate that overall attrition is no higher than normal. In fact, attrition at Harlem Success Academy 1 since it opened has been slightly less than that of its peers.
For more information on the Success Academy coming to Cobble Hill, visit its website here.
If you are interested in knowing some of the reasons I think the Success Academies have performed so highly, check out my pice on the network here.