One of the great unanswered questions in American education policy is why the major gains we’ve seen on the Nation’s Report Card in the fourth and eighth grades evaporate once students reach the twelfth grade. The 2013 results, released yesterday, demonstrated this phenomenon yet again.

As with all NAEP results, nobody really knows why the scores are up, down, or flat. But when it comes to explaining the lack of meaningful progress at the high school level, here are the leading guesses:

*It’s because of our changing demographics. Schools are getting better, but they are facing the headwinds of an increasingly diverse student body. (As Hispanic students replace white students, their generally lower scores weigh down national averages.) That appears to be the case for math scores since 2005, where gains for whites, blacks, Hispanics, and Asians (all four percentage points or better) outstripped the more meager national average gain of three percentage points. This, however, was not the case for reading, where all subgroup scores are flat or, in the case of African Americans, down since 1992.
*It’s because of our increasing graduation rates. It’s true that our graduation rates have risen significantly in recent years, and it’s almost surely the case that the students who would have dropped out a decade ago but are now sticking it out to get their diplomas are among the lowest performing kids. They may be dragging down our scores.
*It’s because twelfth graders don’t try hard. Some studies indicate that this is a real problem, but I’ve never understood why this would get worse over time.

Those stabs at an answer all serve to explain away our flat scores. But there’s also the possibility that we’re seeing evidence of significant educational problems—namely, the following:

*Our high schools stink. This is the man-on-the-street explanation. We’re raising test scores in elementary and middle schools but not high schools? Duh, it’s because our high schools are terrible and have been largely untouched by reform. There’s surely some truth to that. Take testing and accountability, for example. Annual assessments stop in the eighth grade; teacher value-added scores aren’t generally computed at the high school level. Maybe high schools need some of the medicine we’ve been giving the rest of the system.
*We’re sacrificing long-term success for short-term gain. I find this argument intriguing and the most plausible. Simply put: E. D. Hirsch, Jr. is right. If you don’t help kids develop broad content knowledge, especially in elementary school, they will eventually hit a plateau with their reading ability. They will learn to decode and how to use various “comprehension strategies,” but they won’t become expert readers because they won’t be able to make sense of the texts they are encountering. And our practice of holding schools (and now teachers) accountable for year-to-year gains on reading tests only encourages them to focus on things that might get a short term bump (skills and strategies) and ignore the things that will make an impact over the long-term (such as content knowledge). It’s like companies who obsess over quarterly results to the detriment of long-term sustainability.

Let me be clear (lest I am accused of mis-NAEP-ery): I don’t know which, if any, of these explanations are on target. Graduate students: This is an area ripe for study. And Arne Duncan: If you want to do something constructive with your remaining eighteen months in office, how about empaneling a commission of smart people to try to figure this out? Such a fundamental aspect of our educational system—stagnation at the high school level—should not remain a mystery forever.

-Michael Petrilli