Charter Schools vs. Public Schools: Student Achievement Compared

Introduction and Study Overview

This paper examines three major studies that compare the performance of charter schools to that of traditional public schools in the United States. Each study is summarized and then evaluated for the strength and defensibility of its data and conclusions.

Student-Teacher Ratios in Charter and Public Schools

Charter Schools 2000: Fourth Year Report

This study makes the central assumption that the student-to-teacher ratio in a school correlates with the quality of education students receive — specifically, that a lower ratio indicates a stronger school.

In 1998–99, most charter schools had a slightly lower student-to-teacher ratio than all public schools in the 27 charter states (using 1997–98 data). The median student-to-teacher ratio for charter schools was 16.0, compared to 17.2 for all public schools (Fourth Year, 1).

The disparity between charter schools and all public schools in the median student-to-teacher ratio was approximately two students per teacher at the primary, K–12, and "other" grade levels. The gap was less than one at the elementary, K–8, middle, middle-high, and high school levels (ibid).

The most extreme disparity appeared at the ungraded school level, where ungraded charter schools had a much higher student-to-teacher ratio — 18.8 students per teacher — compared to just 8.8 students per teacher in other public schools (ibid).

A higher proportion of all public schools had student-to-teacher ratios in the mid-range (16–20 students per teacher), while charter schools were more likely to have both smaller and larger class sizes. Some instances of high student-to-teacher ratios in charter schools — especially at the high school level — may reflect the use of non-traditional educational approaches such as self-paced computer-assisted instruction and distance learning (ibid).

The research was conducted using data from a large percentage of both public and charter schools, which lends credibility to the findings. However, one of the study's most significant limitations is the foundational assumption that student-to-teacher ratio directly reflects school quality and educational quality — a claim that is not without debate.

Harvard Study on Charter School Academic Achievement

Achievement in Charter Schools and Regular Public Schools in the United States: Understanding the Differences — December 2004

In this study, Caroline Hoxby finds that charter schools perform better than general public schools after accounting for a number of data limitations. The study finds that a higher percentage of students in established charter schools are judged proficient on state reading and math examinations than at the nearest traditional public school.

If a charter school has been operating for more than nine years, ten percent more students score at or above the proficiency level in both subjects. For charter schools in operation for five to eight years, five percent more students reach reading proficiency compared to their public school peers (Harvard, 1). The advantage in math is four percent. For charter schools that have been operating between one and four years, the reading advantage is 2.5%. Overall, charter school students are five percent more likely to be proficient in reading and three percent more likely to be proficient in math on their state exams (Harvard, 1).

The most defensible finding from this study is that ten percent more students score at or above the proficiency level when a charter school has been operating for more than nine years. This is a substantial and meaningful difference.

However, the differences of four percent and 2.5% appear far less defensible. These figures are barely statistically significant, particularly when compared to the ten-percent figure for longer-established schools. The smaller differences fall well within a standard deviation of the mean and may reflect random variation or a placebo effect rather than a genuine performance advantage.

Conclusion and Critique of the Evidence

Across these three studies, the evidence on charter school performance is mixed and no single conclusion is fully supported. The Fourth Year Report suggests a modest structural advantage for charter schools in staffing ratios, though this rests on a questionable assumption about quality. The Harvard study points to meaningful long-term gains for established charter schools, but its short-term figures are too small to be compelling. The national test score analysis presents the most negative picture of charter school performance, though its political context raises questions about objectivity. Taken together, these studies illustrate the difficulty of reaching definitive conclusions about charter school effectiveness, and they underscore the importance of evaluating both the data and the conditions under which research is produced.

References

"Fourth-Year Report: 2000." (January 2000). U.S. Government Website. Retrieved 10 Jan 2005 at

Harvard University. (2004). "Harvard University and National Bureau of Economic Research: Achievement in Charter Schools and Regular Public Schools in the United States: December 2004." Charter Schools Website. Retrieved 10 Jan 2005 at

Schemo, Jean. (Aug 17, 2004). "Charter Schools Trail in Results: U.S. Data Reveals." New York Times. Section A1. Retrieved 10 Jan 2005 at http://www.nytimes.com/2004/08/17/education/17charter.html