But, you have to look at the data carefully to see that

The new ACT scores are out, and the picture for Kentucky isn’t so great. Overall, the state’s ACT Composite Score did go up 0.1 point for all students across the state’s public, private and home school sectors, but other states are doing better.

One incredible example of a state doing better is Charter-School-Rich Louisiana.

You might want to say, “Hey, how can you say that! Isn’t Kentucky’s 2015 ACT Composite Score average of 20.0 notably better than Louisiana’s 19.4? It is true that when we only consider overall scores, it looks like Kentucky did better than Louisiana, but the overall average scores are hiding something important. Let me explain.

You see, when it comes to comparing state education systems, you cannot accurately find the winners if you only look at overall average scores. If you only look at the overall average scores, you will probably fall into a statistics trap known as Simpson’s Paradox. Let’s expand the Kentucky and Louisiana ACT results for 2015 to see how real data explains Simpson's.

Check out this table, which summarizes data published in Table 1.5 in the 2015 ACT Profile Reports for Kentucky and the separate report for Louisiana.

The top row in the table body shows the overall average scores for “All Students,” which includes all 2015 graduates of each state’s public, private and home school programs combined. Kentucky indeed notably outscores Louisiana for the All Student area.

But, take a look at what happens when we break the data out by race. As shown by the table cells highlighted in yellow, Louisiana outscores Kentucky for every separate racial group the ACT reports except for the very small numbers of Native Hawaiians/Other Pacific Islanders found in each state.

Now who looks like the education winner? Obviously, it is Louisiana.

The only reason Kentucky looks like a winner when we only look at the overall average score for “All Students” is because Kentucky has a lot more white students than Louisiana. Thanks to the grim racial achievement gaps, only examining overall scores makes Kentucky look better only because the Bluegrass State has a lot more white students even though Kentucky’s whites score notably lower than those in Louisiana.

In fact, if the student racial mix in Louisiana had the same proportions found in Kentucky, I calculate that Louisiana’s average ACT Composite Score would be 20.4, notably higher than Kentucky’s.

The clearly better performance in Louisiana for virtually all racial groups has important messages for Kentucky regarding charter schools. Keep in mind that Louisiana had to essentially rebuild much of the Southern half of the state’s school system after Hurricane Katrina hit a decade ago. Louisiana chose to do that with a large number of charter schools, and the impact of that decision for school choice is clearly bearing fruit.

So, why does Kentucky continue to fight the growing evidence? School choice does do a better job for students, something we badly need here. The argument for choice just keeps growing, and even the ACT results add support, provided you remember the cardinal rule – never rank state education systems based only on overall average scores. You have to dig deeper to overcome the seriously different racial mixes that are now found in different states across the nation. Otherwise, you run the real risk of becoming the next person to fall prey to Simpson’s Paradox.