The charter school study released this week that suggests charter school students are catching up with their suburban peers leaves many questions unanswered. As GothamSchools and the New York Times reported, the study found that a student who attended a charter school for all of grades K-8 would close approximately 86 percent of the “Scarsdale-Harlem achievement gap” in math and 66 percent of the achievement gap in English.

But here’s what I want to know.

1. How many students in the study actually completed grades K-8 in charter schools? Nowhere in the study does it say. Yet these students supposedly close 86 percent of the Scarsdale-Harlem achievement gap in math and 66 percent in ELA. It would help to know how many there are.

2. How many students were in charter schools for two, three, four, five, or more consecutive years? Nowhere in the study does it say.

3. For that matter, how many students in the study were in charter schools? Nowhere in the study does it say. It states that “the current report covers 93 percent of New York City’s charter school students who were in test-taking grades between 2000-01 and 2007-08,” but it does not give numbers for those grades.

4. How many charter school students took tests each year? Nowhere in the study does it say. It gives the number of charter school applicants who took tests in each grade between 2000-01 and 2007-08 (combined), but it does not break down these numbers into “lotteried-in” and “lotteried-out” categories. Nor does it say how many took the tests each year, or how many took them in charter schools for consecutive years.

5. How many students (charter or public school) in the study switched schools within the same school type, e.g., charter to charter or public to public? Nowhere in the study does it say. This is important. We should consider the difference between stable and unstable learning conditions.

6. How many students who started out in the study were no longer in it by the end? About 14 percent of charter school students in the study transferred to regular public schools. It appears that another 24.8 percent of students left the study for other reasons (moving to the suburbs or transferring to a private school; graduated from high school; etc.). It is not entirely clear whether these two groups are discrete. If they are, then nearly 40 percent of charter school students in the study did not remain in charter schools for the duration of the study.

7. How many charter schools have existed long enough for a student to have attended grades K-8 (or K-5, or as long as the school extends)? Nowhere in the study does it say.

8. Which schools did the “lotteried-out” students attend? Nowhere in the study does it say. If they were in troubled, overcrowded, or dangerous schools, then this could affect the results.

We are left with many unknowns. We do not know how many students remained in charter schools for two, three, four, or more consecutive years. We know nothing about the schools that the “lotteried-out” students attended; we don’t even know whether they remained in the same public schools for the duration of the study. But if I were to raise my hand and ask one (two-part) question, I’d ask (a) how many students were in charter schools for grades K-8 and (b) their ratio to the total charter school population. If they are a hypothetical group, the study should make that clear.

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