Achievement Gap in AISD and IDEA Charter Schools

Posted on December 17, 2011


The achievement gap is generally considered to refer to the gap in achievement between two groups of students as measured by test scores. Other measures of the achievement gap include dropout rates, high school completion rates, and college-going rates. Generally, however, the phrase refers to test scores.

One rationale for expanding charter schools is that such schools can help close the achievement gap. For example, the IDEA website claims, ” Closing the achievement gap is no longer a phrase, but a reality at IDEA Public Schools.” Yet, no data is provided that substantiates this claim. In fact, a search of the Texas Charter School Association, IDEA Charter school website, and a general google search for “achievement gap Texas charter schools” and “Texas charter schools closing achievement gap” did not yield a single result of the closing of the achievement gap. Hopefully, I simply missed the documentation and someone can point me to the evidence.

Because I could find no evidence, I decided to use student-level data from the Texas Education Agency to examine the achievement gap between students not participating in the federal free-/reduced-price lunch program and students participating in the federal free-/reduced-price lunch program in mathematics and reading pm the Texas Assessment of Knowledge and Skills (TAKS) in the 2010-11 school year. Further, I examined the data for all grade levels and for all schools enrolling at least 60% economically disadvantaged students. I chose the 60% cut point because all IDEA Charter Schools enroll at least 60% economically disadvantaged students.

Most organizations–including state education agencies and school districts–calculate the achievement gap incorrectly. Take for example, Austin ISD. In the AISD “State of the District” report, AISD claims the achievement gap has decreased by pointing out that the percentage of students passing the TAKS tests between White and non-White students has decreased over time.

Yet, as Daniel Koretz clearly explains in his book entitled “Measuring Up: What Educational Testing Really Tells Us,” using the percentage of students passing/proficient always provides an inaccurate assessment of the achievement gap. Other experts in this area concur. I strongly suggest reading his very easy to digest book top understand why we must use scale scores and, better yet, z-scores to assess the achievement gap.

Below I present the achievement gap in z-scores which are very similar to standard deviations.* A positive number indicates that not economically disadvantaged students outperform economically disadvantaged students and a negative number would indicate that not economically disadvantaged students were outperformed by economically disadvantaged students. The magnitude of the number indicates the size of the achievement gap. Thus, a result of .25 indicates a smaller achievement gap than a result of .75. The closer to 0 the result, the smaller the achievement gap.

As shown below, AISD has not closed the achievement gap. but neither has IDEA Charter Schools, nor all Texas schools. In most, but not all cases, the gap for IDEA schools is smaller than for AISD schools. Yet, the gap remains relatively large for IDEA Charter schools at most grade levels.

Table 1: TAKS Achievement Gaps in Mathematics and Reading (2011) for Austin ISD, IDEA Charter Schools, and all Texas Schools with at Least 60% Economically Disadvantaged Students

DATA SOURCE: Student-level TAKS data from TEA; Analysis: Ed Fuller

So, what can we conclude from this table?

First, IDEA Charter Schools have NOT closed the achievement gap between low-income and not low-income students and are not particularly close to doing so.

Second, IDEA Charter Schools generally have a smaller achievement gap than AISD schools. However, one would need to investigate the effect of students leaving each set of schools to further substantiate this claim.

Third, despite the claims of IDEA leaders that poverty does not matter and does not influence achievement, poverty clearly has a negative effect on achievement–even in IDEA Charter Schools. If poverty did not matter, there would be no achievement gap in IDEA Charter Schools. That poverty affects achievement is one of the most consistent findings in education research. It is next to impossible to find any quality study that finds otherwise.

* I calculated the gap by first calculating the z score for all students for each grade level with TAKS results. The z-score was calculated by calculating the mean, then dividing by the standard deviation. The achievement gap was then calculated for IDEA Charter Schools, AISD schools, and all Texas schools by subtracting the aggregate z-score for economically disadvantaged students from the aggregate z-score for not economically disadvantaged students, then dividing by the standard deviation for all students.

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