Pick any teacher with more than a decade of experience. Ask that teacher how many educational theories (or "fads" if you will) they have been exposed to over the years. Ask them how many programs, ideas, or philosophies their district has tried. I will guess the average district tries something new about every three years. My district certainly fits.
Proponents of this constant change will claim it is the natural outcome of improvement. Each new idea contributes to the greater good. This, of course, ignores the fact that no single one fix has contributed to any statistically significant improvement in any measurable variable. None of it works.
So why do we bother? Why do we seemingly develop a perpetual "flavor of the day"? One reason could be economics. It would be exceedingly profitable for these third-party program developers to "train" our school faculty and staff. They make grand promises, back it up by some limited research that isn't as generalizable as they make it seem, and set a reasonable time frame to measure success. A district will commit to their services for a year or two. At the end of the two years, the district doesn't see significant improvement, so they move on. If they DO get a statistically-significant improvement in some district, they have an immediate case study they can use to market the services. It's a great business model. Hell, maybe I'll do it one of these days.
There could be other reasons. More insidious, conspiratorial reasons. Could the calls for school improvement be a distraction? Could the powers that be (defined however you wish) compel schools to perpetually search for solutions to impossible-to-solve problems to keep them busy?
Let's assume schools serve a useful social purpose in our society. They keep the lower and middle class pacified so they don't kill the rich. Yes, it's a bit of a Marxist idea. Since the upper class ultimately control public schools (via legislation and lobbying among other methods), they have the power to call for continual improvement (NCLB?) This forces schools to fix problems that are inherent in the system. The problems cannot be solved. Keeping the bureaucracy within schools busy in this "pot of gold" search keeps us from coming to the conclusion that the schools are not broken, they work exactly like they are designed to work.
We're hamsters in a glass cage running around a wheel in an attempt to escape. It gives us a false hope that escape is possible if we try hard enough. And it keeps us busy enough to avoid asking why we're in the cage in the first place.