Anyone who follows education policy debates might hear the term “standard deviation” fairly often. Most people have at least some idea of what it means, but I thought it might be useful to lay out a quick, (hopefully) clear explanation, since it’s useful for the proper interpretation of education data and research (as well as that in other fields).
Many outcomes or measures, such as height or blood pressure, assume what’s called a “normal distribution.” Simply put, this means that such measures tend to cluster around the mean (or average), and taper off in both directions the further one moves away from the mean (due to its shape, this is often called a “bell curve”). In practice, and especially when samples are small, distributions are imperfect — e.g., the bell is messy or a bit skewed to one side — but in general, with many measures, there is clustering around the average.
Let’s use test scores as our example. Suppose we have a group of 1,000 students who take a test (scored 0-20). A simulated score distribution is presented in the figure below (called a “histogram”). Read More »
One of the purely presentational aspects that separates the new “generation” of CREDO charter school analyses from the old is that the more recent reports convert estimated effect sizes from standard deviations into a “days of learning” metric. You can find similar approaches in other reports and papers as well.
I am very supportive of efforts to make interpretation easier for those who aren’t accustomed to thinking in terms of standard deviations, so I like the basic motivation behind this. I do have concerns about this particular conversion — specifically, that it overstates things a bit — but I don’t want to get into that issue. If we just take CREDO’s “days of learning” conversion at face value, my primary, far more simple reaction to hearing that a given charter school sector’s impact is equivalent to a given number of additional “days of learning” is to wonder: Does this charter sector actually offer additional “days of learning,” in the form of longer school days and/or years?
This matters to me because I (and many others) have long advocated moving past the charter versus regular public school “horserace” and trying to figure out why some charters seem to do very well and others do not. Additional time is one of the more compelling observable possibilities, and while they’re not perfectly comparable, it fits nicely with the “days of learning” expression of effect sizes. Take New York City charter schools, for example. Read More »
In 2009, The New Teacher Project (TNTP) released a report called “The Widget Effect.” You would be hard-pressed to find too many more recent publications from an advocacy group that had a larger influence on education policy and the debate surrounding it. To this day, the report is mentioned regularly by advocates and policy makers.
The primary argument of the report was that teacher performance “is not measured, recorded, or used to inform decision making in any meaningful way.” More specifically, the report shows that most teachers received “satisfactory” or equivalent ratings, and that evaluations were not tied to most personnel decisions (e.g., compensation, layoffs, etc.). From these findings and arguments comes the catchy title – a “widget” is a fictional product commonly used in situations (e.g., economics classes) where the product doesn’t matter. Thus, treating teachers like widgets means that we treat them all as if they’re the same.
Given the influence of “The Widget Effect,” as well as how different the teacher evaluation landscape is now compared to when it was released, I decided to read it closely. Having done so, I think it’s worth discussing a few points about the report. Read More »
The U.S. Department of Education has released a very short, readable report on the comparability of value-added estimates using two different tests in Indiana – one of them norm-referenced (the Measures of Academic Progress test, or MAP), and the other criterion-referenced (the Indiana Statewide Testing for Educational Progress Plus, or ISTEP+, which is also the state’s official test for NCLB purposes).
The research design here is straightforward – fourth and fifth grade students in 46 schools across 10 districts in Indiana took both tests, their teachers’ value-added scores were calculated, and the scores were compared. Since both sets of scores were based on the same students and teachers, this is allows a direct comparison of how teachers’ value-added estimates compare between these two tests. The results are not surprising, and they square with similar prior studies (see here, here, here, for example): The estimates based on the two tests are moderately correlated. Depending on the grade/subject, they are between 0.4 and 0.7. If you’re not used to interpreting correlation coefficients, consider that only around one-third of teachers were in the same quintile (fifth) on both tests, and another 40 or so percent were one quintile higher or lower. So, most teachers were within a quartile, about a quarter of teachers moved two or more quintiles, and a small percentage moved from top to bottom or vice-versa.
Although, as mentioned above, these findings are in line with prior research, it is worth remembering why this “instability” occurs (and what can be done about it). Read More »
Virtually all discussions of teacher turnover focuses on teachers leaving schools and/or the profession. However, a recent working paper by Allison Atteberry, Susanna Loeb and James Wyckoff, which was presented at this month’s CALDER conference, reaches a very interesting conclusion using data from New York City: There is actually more movement within NYC schools than between them.*
Specifically, the authors show that, during the years for which they had data (1997-2002 and 2004-2010), over 50 percent of teachers in any given year exhibited some form of movement (including leaving the profession or switching schools), but two-thirds of these moves were within schools – i.e., teachers changing grades or subjects. Moreover, they find that these within-school moves, like those between-schools/professions, appear to have a negative impact on testing outcomes, one which is very modest but statistically discernible in both math and reading.
There are a couple of interesting points related to these main findings. Read More »
In the three most discussed and controversial areas of market-based education reform – performance pay, charter schools and the use of value-added estimates in teacher evaluations – 2013 saw the release of a couple of truly landmark reports, in addition to the normal flow of strong work coming from the education research community (see our reviews from 2010, 2011 and 2012).*
In one sense, this building body of evidence is critical and even comforting, given not only the rapid expansion of charter schools, but also and especially the ongoing design and implementation of new teacher evaluations (which, in many cases, include performance-based pay incentives). In another sense, however, there is good cause for anxiety. Although one must try policies before knowing how they work, the sheer speed of policy change in the U.S. right now means that policymakers are making important decisions on the fly, and there is great deal of uncertainty as to how this will all turn out.
Moreover, while 2013 was without question an important year for research in these three areas, it also illustrated an obvious point: Proper interpretation and application of findings is perhaps just as important as the work itself. Read More »
In a post earlier this week, I noted how several state and local education leaders, advocates and especially the editorial boards of major newspapers used the results of the recently-released NAEP results inappropriately – i.e., to argue that recent reforms in states such as Tennessee and D.C. are “working.” I also discussed how this illustrates a larger phenomenon in which many people seem to expect education policies to generate immediate, measurable results in terms of aggregate student test scores, which I argued is both unrealistic and dangerous.
Mike G. from Boston, a friend whose comments I always appreciate, agrees with me, but asks a question that I think gets to the pragmatic heart of the matter. He wonders whether individuals in high-level education positions have any alternative. For instance, Mike asks, what would I suggest to Kevin Huffman, who is the head of Tennessee’s education department? Insofar as Huffman’s opponents “would use any data…to bash him if it’s trending down,” would I advise him to forego using the data in his favor when they show improvement?*
I have never held any important high-level leadership positions. My political experience and skills are (and I’m being charitable here) underdeveloped, and I have no doubt many more seasoned folks in education would disagree with me. But my answer is: Yes, I would advise him to forego using the data in this manner. Here’s why. Read More »
A couple of months ago, Bill Gates said something that received a lot of attention. With regard to his foundation’s education reform efforts, which focus most prominently on teacher evaluations, but encompass many other areas, he noted, “we don’t know if it will work.” In fact, according to Mr. Gates, “we won’t know for probably a decade.”
He’s absolutely correct. Most education policies, including (but not limited to) those geared toward shifting the distribution of teacher quality, take a long time to work (if they do work), and the research assessing these policies requires a great deal of patience. Yet so many of the most prominent figures in education policy routinely espouse the opposite viewpoint: Policies are expected to have an immediate, measurable impact (and their effects are assessed in the crudest manner imaginable).
A perfect example was the reaction to the recent release of results of the National Assessment of Educational Progress (NAEP). Read More »
As reported over at Education Week, the so-called “sequester” has claimed yet another victim: The National Assessment of Educational Progress, or NAEP. As most people who follow education know, this highly respected test, which is often called the “nation’s report card,” is a very useful means of assessing student performance, both in any given year and over time.
Two of the “main assessments” – i.e., those administered in math and reading every two years to fourth and eighth graders – get most of the attention in our public debate, and these remain largely untouched by the cuts. But, last May, the National Assessment Governing Board, which oversees NAEP, decided to eliminate the 2014 NAEP exams in civics, history and geography for all but 8th graders (the exams were previously administered in grades 4, 8 and 12). Now, in its most recent announcement, the Board has decided to cancel its plans to expand the sample for 12th graders (in math, reading, and science) to make it large enough to allow state-level results. In addition, the 4th and 8th grade science samples will be cut back, making subgroup breakdowns very difficult, and the science exam will no longer be administered to individual districts. Finally, the “long-term trend NAEP,” which has tracked student performance for 40 years, has been suspended for 2016. These are substantial cutbacks.
Although its results are frequently misinterpreted, NAEP is actually among the few standardized tests in the U.S. that receives rather wide support from all “sides” of the testing debate. And one cannot help but notice the fact that federal and state governments are currently making significant investments in new tests that are used for high-stakes purposes, whereas NAEP, the primary low-stakes assessment, is being scaled back. Read More »
A new report from CREDO on charter schools’ test-based performance received a great deal of attention, and rightfully so – it includes 27 states, which together serve 95 percent of the nation’s charter students.
The analysis as a whole, like its predecessor, is a great contribution. Its sheer scope, as well as a few specific parts (examination of trends), are new and important. And most of the findings serve to reaffirm the core conclusions of the existing research on charters’ estimated test-based effects. Such an interpretation may not be particularly satisfying to charter supporters and opponents looking for new ammunition, but the fact that this national analysis will not settle anything in the contentious debate about charter schools once again suggests the need to start asking a different set of questions.
Along these lines, as well as others, there are a few points worth discussing quickly. Read More »
A correlation between two variables measures the strength of the linear relationship between them. Put simply, two variables are positively correlated to the extent that individuals with relatively high or low values on one measure tend to have relatively high or low values on the other, and negatively correlated to the extent that high values on one measure are associated with low values on the other.
Correlations are used frequently in the debate about teacher evaluations. For example, researchers might assess the relationship between classroom observations and value-added measures, which is one of the simpler ways to gather information about the “validity” of one or the other – i.e., whether it is telling us what we want to know. In this case, if teachers with higher observation scores also tend to get higher value-added scores, this might be interpreted as a sign that both are capturing, at least to some extent, “true” teacher performance.
Yet there seems to be a tendency among some advocates and policy makers to get a little overeager when interpreting correlations. Read More »
Education researchers have paid a lot of attention to the sorting of teachers across schools. For example, it is well known that schools serving more low-income students tend to employ teachers who are, on average, less qualified (in terms of experience, degree, certification, etc.; also see here).
Far less well-researched, however, is the issue of sorting within schools – for example, whether teachers with certain characteristics are assigned to classes with different students than their colleagues in the same school. In addition to the obvious fact that which teachers are in front of which students every day is important, this question bears on a few major issues in education policy today. For example, there is evidence that teacher turnover is influenced by the characteristics of the students teachers teach, which means that classroom assignments might either exacerbate or mitigate mobility and attrition. In addition, teacher productivity measures such as value-added may be affected by the sorting of students into classes based on characteristics for which the models do not account, and a better understanding of the teacher/student matching process could help inform this issue.
A recent article, which was published in the journal Sociology of Education, sheds light on these topics with a very interesting look at the distribution of students across teachers’ classrooms in Miami-Dade between 2003-04 and 2010-11. The authors’ primary question is: Are certain characteristics, most notably race/ethnicity, gender, experience, or pre-service qualifications (e.g., SAT scores), associated with assignment to higher or lower-scoring students among teachers in the same school, grade, and year? Read More »
Our guest author today is Ian Robinson, Lecturer in the Department of Sociology and in the Residential College’s interdisciplinary Social Theory and Practice program at the University of Michigan.
I ended my previous post by arguing that (1) if teaching is at least as valuable as research, and (2) nontenure-track (NTT) faculty teach at least as well as tenure-track (TT) faculty, then the very large pay disparities between the two classes of faculty that characterize American universities today violate a basic principle of workplace fairness: equal pay for equal work. When conditions (1) and (2) are met, then, all an institution can do to defend current practice is plead poverty: we can’t afford to do what we ourselves must acknowledge to be “the right thing.”
But what about places like the University of Michigan-Ann Arbor, where I work? Is condition (1) met in what are sometimes called “R1” universities like mine? If not, maybe big pay disparities are warranted by the fact that, in such universities, research is a much higher institutional priority than undergraduate teaching. If teaching is a low enough priority, current pay inequalities could be justified by the fact that NTT faculty are not paid to do research and publishing – even though many of them do it – and, conversely, that most TT faculty pay is for their research and publishing, rather than their teaching. Read More »
** Reprinted here in the Washington Post
A big part of successful policy making is unyielding attention to detail (an argument that regular readers of this blog hear often). Choices about design and implementation that may seem unimportant can play a substantial role in determining how policies play out in practice.
A new paper, co-authored by Elizabeth Davidson, Randall Reback, Jonah Rockoff and Heather Schwartz, and presented at last month’s annual conference of The Association for Education Finance and Policy, illustrates this principle vividly, and on a grand scale: With an analysis of outcomes in all 50 states during the early years of NCLB.
After a terrific summary of the law’s rules and implementation challenges, as well as some quick descriptive statistics, the paper’s main analysis is a straightforward examination of why the proportion of schools meeting AYP varied quite a bit between states. For instance, in 2003, the first year of results, 32 percent of U.S. schools failed to make AYP, but the proportion ranged from one percent in Iowa to over 80 percent in Florida.
Surprisingly, the results suggest that the primary reasons for this variation seem to have had little to do with differences in student performance. Rather, the big factors are subtle differences in rather arcane rules that each state chose during the implementation process. These decisions received little attention, yet they had a dramatic impact on the outcomes of NCLB during this time period. Read More »
** Reprinted here in the Washington Post
Last week, I attended a Center for American Progress (CAP) discussion, where UC Berkeley professor David Kirp spoke about his research on Union City’s school system, and offered some ideas from his new book, Improbable Scholars: The Rebirth of a Great American School System and a Strategy for America’s Schools.
Kirp’s work and Union City have received a lot of attention in the last month or so, and while most find the story heartening, a few commentators have had more skeptical reactions. True, this is the story of one district in one state finding success through collaboration and hard work, but research from other disciplines – sociology, business, management, organizational studies – suggests that similar human dynamics can be observed in settings other than schools and school districts. I would like to situate Kirp’s work in this broader framework; that is, among a myriad of studies – case studies, if you will – pointing to the same fundamental phenomena.
Union City is a community with an unemployment rate 60 percent higher than the national average, where three-quarters of public school students live in homes where only Spanish is spoken. About 25 years ago, the school district was in so much trouble that state officials threatened a state takeover. Since then, Union City’s measured performance has improved considerably. In 2011, almost 90 percent of the district’s students graduated from high school, and 60 percent went on to college. The change is large enough to suggest some degree of “real” improvement, and it’s plausible to believe that better school quality had at least something to do with that. So, what was Union City’s school improvement strategy? Read More »