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I was very interested to read the UFT’s latest report on charter school attrition in middle schools, as I’ve had trouble finding reliable statistics to track charter school students from year to year. The UFT report claims that state test data provides a fairly accurate method to track charter school attrition-that is, the number of students that leave a charter school. However, the report doesn’t provide data on the number of students that a particular charter school decides to hold back, or “retain.” Therefore, it can only provide information on testing cohort attrition — that is, the number of students that vanish from a testing group from year to year.

I augmented the state test data with the numbers on retained students, which are available from the Basic Education Data System. (For more on BEDS, see this post.) The UFT report states:

If students are being left back, then their entrance into the cohort of the lower grade should be reflected in the size of that cohort. That cohort might grow, for example. What happens instead, however, is that those cohorts too are generally shrinking as students move up in grades. Since the cohorts into which the vanishing students would be assigned are themselves shrinking, retention seems unlikely to be the major factor in cohort attrition.

I confirmed with Jackie Bennett, the author of the UFT report, that she did not look at the BEDS data on retained students. This means that she couldn’t consider retention from earlier grades that would reduce the numbers in these same cohorts. I found that when you consider the number of students retained each year in each grade, the majority of testing cohort attrition actually is due to retention of large numbers of students in both fifth and sixth grade.

The UFT report featured four charter schools in its comparative analysis: Williamsburg Collegiate Charter School, Harlem Village Academy, Leadership Village Academy, and KIPP S.T.A.R. charter school. According to BEDS data filed with the state, each of the schools retained a large number of students in their entering classes in each year. I don’t have data for 2005-2006 (the first year of the UFT study) but in 2006-2007, Williamsburg Collegiate retained 19 fifth-graders, Harlem Village academy retained 13, Harlem Village Leadership Academy retained 18, and KIPP S.T.A.R. retained 10. These are roughly the number of students that the UFT test data shows were lost to attrition over the three-year period from 2006-2007 to 2008-2009.

In the case of Williamsburg Collegiate, the school actually retained more students than it lost over the time period studied, which could indicate that the school accepted students off of the waitlist to augment the initial fifth-grade cohort. This again questions the usefulness of using state test data to determine whether the same students are staying in charter schools over the span of their middle school years.

The way the UFT looked at the numbers wasn’t wrong. But adding retention to the equation changes the story. The real story might be that the schools are producing higher test scores not because many students leave but because they require many students to repeat a grade.

I hope in the future that the New York State Education Department, the city Department of Education, or charter schools themselves will make overall school attrition data more readily available. Currently, I know of no publicly available data that gives a good sense of charter school attrition over time. I welcome any suggestions from charter school operators or researchers for approaches that could provide more accurate numbers.