I'm not an expert, and hopefully somebody with more "inside ball" knowledge on this can fill in better... but....
One of the guys I go fishing with is a math teacher, and he explained it to me this way. In Washington, there are overall curriculum standards set by the state. Districts are free to choose specific teaching curricula, as long as they fit in the "box" defined by the state.
According to my buddy, the math teacher, the standards in this state (the curriculum “box”) are predicated upon the notion that everybody should aspire to be an astrophysicist. Smart math teachers recognize that not everybody is that smart, or that driven, or that drawn to a career that is so math intensive.
They'd rather have an array of options to teach relevant math for students with a variety of different career and educational goals and realities in mind.
Say you've got a group of kids who are going to be English majors, and a group of kids who are probably going to join the Coast Guard and be rescue swimmers. They don't need to know the building blocks of math theory that will lead them to be the next Stephen Hawking. They need more practical knowledge and less of the theoretical building blocks (How much fuel should I put in the rescue helicopter? How big of an advance should I ask for to write my new novel?), but this "box" the State requires math curriculum to fit in doesn't allow for this.
Instead, the State's curriculum "box" requires that everybody shoot for the stars and learn building blocks that will help them one day master quantum mechanics.
THIS is the problem that leads districts to jump from "fad to fad" as Dr. Mass says, because this "discovery math" nonsense is utterly useless for the future writer and rescue swimmer, but can be immensely valuable as a series of building blocks in creating a deep theoretical understanding of advanced calculus and astrophysics.
For the majority of kids in our public schools, it's completely useless. But because the state defined "box" for math curriculum aims to get everybody to that top tier of mastery of Ph.D. level theoretical mathematics, districts are inclined to choose methods that pursue this asinine state defined goal.
A smarter approach, according to my friend the math teacher, would be to get rid of the State bent that everybody teach to the top, and instead create several tracks.
Track 1 is for the future chefs, writers, police officers and art teachers. They need less theory, more practical math. They’re probably 60% of the population.
Track 2 is for the future actuaries, insurance adjusters, finance bankers, accountants and civil engineers. They need deeper theoretical understandings to build on because they will take their math learning further. They’re probably 30% of the population.
Track 3 is for the future Stephen Hawkings, the future astrophysicists, NASA rocket propulsion engineers, and developers of cold fission power. These people, probably 10% or less of today's students, are the few that actually benefit from this "Discovery math" and whatnot that teaches them to understand what they're doing, instead of focusing on the right answer. Because they will someday take their math skills to the proverbial Mt. Everest of mathematics, they actually benefit from the current methods that focus on building theoretical understandings rather than getting correct answers
The problem is that in this state districts are required to aim for all students to be that 10%, so they are drawn to curricula that are useless for the 90% of students because the state says everybody has to aim for the top.
It's nonsense. As a state, we need to come to terms with the fact that a Boeing Aeronautical engineer will need to know more of the theoretical underpinnings of math than a firefighter. But we're not allowed to do that, so districts jump from fad to fad trying to get everybody to reach this mythical peak of theoretical math knowledge.
At least that's what my buddy the math teacher says when we're out fishing. I could be wrong, I'm just a fisherman and a writer. I know I need to mix oil to gasoline at 50:1 in a 2 cycle outboard, and that's good enough for me, because I don't plan on redefining quantum mechanics.