Governors and ex-governors who are now running for president (think Wisconsin’s Scott Walker of Wisconsin, Maryland’s Martin O’Malley, and Louisiana’s Bobby Jindal) love to talk about how their policies have helped boost test scores, hike graduation rates, or increase Advanced Placement passing rates.

So did any of the nine-governors-turned-presidential candidates really have a stellar standout record when it comes to K-12 policy? The short answer is that there are no obvious superstars. The longer, green-eye shade answer? It’s really tough to say.

It’s nearly impossible for anyone (except maybe a teacher, building principal, or possibly a district superintendent) to truly claim credit for moving the needle on student achievement. Without the gold standard of research, a randomized control trial where some students get the “treatment” (say, access to a new pre-kindergarten program) and others don’t, it’s tough to say for sure whether a particular policy really contributed to a bump in test scores, according to the experts.

Plus, if a policy trend is happening nationally, such as improved graduation rates, it’s hard for policymakers to claim credit for it in their states.

You can read more about all the asterisks candidates should attach to their edu-claims in this story. And compare how students in their states did on the National Assessment of Educational Progress or NAEP, above. For a further apples-to-apples comparison of the various edu-records of the governors and former governors who are hoping to take the White House, go here.