Yesterday, Jonah went off to his first day of 6th grade at our local middle school. After some grumpiness about being forced to wear a "nice shirt" to school on the first day, he ran off with his buddies and walked to school. I crossed my fingers that he learns something this year. Education Next reports that children who attend a middle school do poorer on test scores than children who attend a K-8 school. (via Joanne Jacobs)

… students who enter public middle schools in New York City fall behind
their peers in K–8 schools.  This is true both for math and English
achievement. Even more troubling, the middle-school disadvantage grows
larger over the course of the middle-school years. With the transition
into a middle school, students set out on a trajectory of lower
achievement gains.

It's an extensive study with great graphs about what happens to student achievement when kids leave the protective nest of elementary school and enter the state of nature in the middle school cafeteria. 

They are honest about the fact that they can't quite explain why kids do better in a K-8 school, rather than a middle school.

Given the data we have, we can only speculate about why it is harder to
educate middle school–aged students in large groups. Developmental
psychologists have shown that adolescent children commonly exhibit
traits such as negativity, low self-esteem, and an inability to judge
the risks and consequences of their actions, which may make them
especially difficult to educate in large groups. The combining of
multiple elementary schools and their students also disrupts a student’s
immediate peer group. And middle schools often serve a more diverse
student population than many students encountered in elementary school.
Yet while it seems plausible that these changes in environment would
matter, we could not find any evidence in our data that any one
hypothesis can explain the drop in learning among students moving to
middle schools.

My guess is that by isolating the most obnoxious, peer-obsessed, hyper-hormoned, Justin Bieber-obsessed children in one school, their worst tendencies are amplified. Also, teachers treat K-8 kids like children, but in a middle school, they treat them like the enemy. 

This is a really interesting study that should be replicated and expanded. The problem is that there is no way to change course on middle schools. The buildings have been built. The administrators are hired.