As Kansas Republicans look to Texas as a role model for Kansas to follow, defenders of high levels of school spending in Kansas characterize Texas schools as inferior to Kansas schools.
A recent tweet from the Kansas Democratic Party read “Fun Texas Fact #6 for @govsambrownback: 28% of TX 4th graders read proficiently, 39th nationally. KS = 36%, 12th. #ksleg #KansasIsNotTexas”
— KS Democratic Party (@KansasDems) January 18, 2013
Superficially, it looks like the Kansas Democrats might be right. Scores on the National Assessment of Education Progress, a test that is the same in all states, has Kansas scoring better than Texas (with one tie) in reading and math, in both fourth and eighth grade.
Considering only fourth grade reading, and looking at the percent reading at the “proficient” level or better, the statistics cited by the Kansas Democrats are absolutely correct.
That makes sense to the Democrats and to the school spending establishment, as Kansas, in 2009, spent $11,427 per student. Texas spent $11,085, according to the National Center for Education Statistics. Considering only spending deemed by NCES to be for instruction, it was Kansas at $6,162 per student and Texas at $5,138.
Texas also has larger class sizes, or more precisely, a higher pupil/teacher ratio. Texas has 14.56 students for each teacher. In Kansas, it’s 13.67. (2009 figures, according to NCES.)
So for those who believe that spending a lot on schools is necessary for student success, Kansas and Texas NAEP scores are evidence that they’re correct in their belief.
But let us take another look at the Kansas and Texas NAEP scores. Here’s a table of 2011 scores for fourth grade reading, the subject and grade level the Democrats used. (Click on the table to open it in a window by itself.)
Notice that when reporting scores for all students, Kansas does better than Texas. Kansas has the highest scale score, and higher percentages of students meeting each level of achievement. (The cell with the best value is shaded.)
But when we look at subgroups, all the sudden the picture is different: Texas almost always bests or ties Kansas.
Kansas students have better reading scores than Texas students, that is true. It is also true that Texas white students have better reading scores than Kansas white students, Texas black students score better than or equal to Kansas black students, and Texas Hispanic students score almost exactly the same as Kansas Hispanic students.
How can this be? How can it be that when considering all students, Kansas does better than Texas, but when looking at ethnic subgroups, the situation is mostly reversed?
The answer is Simpson’s Paradox. A Wikipedia article explains: “A paradox in which a trend that appears in different groups of data disappears when these groups are combined, and the reverse trend appears for the aggregate data.”
In this case, the confounding factor (“lurking” variable) is that the two states differ greatly in the proportion of white students. In Kansas, 68 percent of students are white. In Texas it’s 31 percent. This large difference in the composition of students is what makes it look like Kansas students perform better on the NAEP than Texas students.
But looking at the scores for ethnic subgroups, which state would you say has the most desirable set of NAEP scores?