This caveat about the recently released 2012 PISA scores (aka the Program for International Student Assessment) is really important. The same caveat applies to the PIAAC numbers on adult skills that were released in October:

Do not confuse correlation with causation. This is a point we’ve made repeatedly with national and international test results, but it’s worth reiterating here. Since PISA was released this morning, I’ve gotten dozens of emails from advocacy groups saying the results bolster or repudiate whatever policies they support or eschew (the Common Core State Standards, early childhood ed, high-stakes testing, poverty-reduction efforts, teacher preparation, etc.). But, as several sources point out in my story, the results do not explain why particular countries performed a certain way, only that they did. Even the experts most skilled at talking about PISA test scores can quickly fall into the causation trap, so please take this caveat to heart. (my emphasis)

This point has been rarely made during the many PIAAC presentations that I have endured had the pleasure of viewing. Assessments like PISA and PIAAC tell you the “what” (assuming you find them credible) but not the “why.” Responses to such assessments should be based on reasonable evidence as to the “why,” otherwise they are essentially shots in the dark.