My parents were both teachers for ~30 years at the high school level here in Illinois.. and then my mother went on to be an educational consultant and inservice provider for another 10 years after retiring from active teaching. As such, I grew up looking at both sides of the educational system more than the average person..
This problem you describe is not new. It's not even something that arose with the poorly named "No Child Left Behind" legislation. I remember Illinois started a program of heavier standardized testing during the early 1990's.. the IGAP tests.. 1993 or 1994 was when I first ran into one in high school.
The teachers at the time were stressed out and annoyed by that.. the tests themselves were abysmal.. I basically "failed" the IGAP "reading comprehension" portion despite getting a 35 out of a possible 36 at the time on the ACT. The next year, one of the better teachers was actually fired in a "scandal" because they released the test early to students to study with. I witnessed many teachers changing their curriculum content to teach directly to these idiotic tests.
Decentralized education, as you mention, can *possibloy* have some benefits.. limited experimentation, etc.. But what I've seen in practice is that it doesn't. What I have seen in practice is some of the most nonsensical bs ever to be invoked in the name of "education."
I speak of the "School Board" system. Whoever thought it was a good idea to have a neighborhood popularity contest between a bunch of disinterested status-seekers with no training or experience in education, and then award the winners collectively with pretty much full administrative control over school operations and curriculum... clearly lived in a different era and/or had mental health issues.
I remember school boards comprised of old religious wingnuts, football obsessed yuppies, and "sky is falling, protect the children" soccer moms. What I do not remember is a single member of the body responsible for education policy having any member upon it actually trained in *education*. As such, the "needs of the community" being represented were "regressive religious indoctrination attempts" and "getting a winning football team" and "don't teach anything remotely controversial"..
Which pretty much results in a completely bullsh*t education. It wasn't just my own school. Every single one I've run into in the surrounding 3 states was similarly disposed.
You can see similar idiocy on a nationwide scale after the Columbine tragedy.. where thousands of school administrators banned the wearing of trench coats in highschools. No rational mind can accept the proposition that trench coats cause violence.. simply because Wall Street is not a daily bloodbath. But it is this kind of knee-jerk, non-thinking decision making which arises from a focus on "the needs of the community", when non-educators make up the "community" representation and have executive authority over the school systems.
Further, the way schools are funded here.. by property taxes.. pretty much guarantees that poor areas desperately in need of resources and better educational opportunities will alreays remain poor and in desperate need, while the rich communities will put in their second olympic sized swimming pool on campus and have Mariott cater their lunchrooms.
During the 30+ years I've been observing things around here.. the "best and brightest" have never thought about becoming teachers.. or if they did, they taught for a year or two, became familiarized with the realities of the job, and left to pursue careers where they weren't abused constantly and could actually reap some rewards.
I'm frankly in favor of centralized education. I'm not, however, in favor of standardized testing or rigid frameworks dependant upon it. However, if one is going to centralize control over education.. it needs to be at a curriculum level, and it needs to be accompanied by centralized *funding*. It's not something that can be slapped in place overnight by an act of Congress.. but it is something that needs to be intelligently evolved over time by a concerted act of national will to improve conditions in our schools.