Another thing that occurred to me recently about "differentiated instruction" (which I've decided to refer to from now on as "discriminatory instruction" until someone can explain to me why it isn't) is that it, like so many other fads that have drifted in and out of the high schools in recent years, is just another way of making high school more like elementary school and less like college.
I don't know exactly when this happened, but some years ago the thinking, at least here in New York, with respect to the high schools was that the best way to improve performance and achievement in high school was to use elementary-school methods in high school classes. Kids complain that school is "boring" and "dull" and "not fun" and they don't like reading or writing or listening to a teacher speak or taking notes or anything like that, so we in turn have to try to make school "fun" by turning academic subject matter into games and physical activities and entertainment, cover the walls with posters and colored paper and fancy borders and cutesy slogans and all manner of colorful eye candy, and of course student work with little gold stars and happy faces on it ... you know, "fun" stuff. Add that to the reflexive blaming of teachers for failing to "make it interesting" or "make it fun" and presto! we turn high school into Romper Room.
(For those of you too young to remember, here's Wikipedia's page on Romper Room. Wonderama is another good one from the same era.)
Using elementary school methods in high school has its occasional utility, obviously. But when the concept of "making learning fun" in this fashion becomes doctrinal or ideological, to the degree that we actively try to make high school as much like elementary school as possible, we approach the point where we defeat the ultimate purpose of upper secondary education. Private high schools are typically called "prep schools;" "prep" as in "preparatory." Public high schools are generally not referred to as prep schools, but their underlying essential purpose is the same: to prepare students for either (a.) higher education, or (b.) employment/entrepreneurship in the real world; or both.
It is just possible that making high school more like elementary school and less like college is a tacit acknowledgment that certain public high school students are not expected to go to college so they don't need to be prepared for it. The implications of this are obvious, and of course no one will ever publicly admit to such a mindset. But even if that's true, for those high school students who do not go to college, high school is the last stop on the educational train before they have to go out into the real world and try to make a life for themselves. I can think of nothing less like the real world than elementary school.
I've always believed that high school should be as much like college as possible, particularly in the upper grades. The intellectual and personal-responsibility skills that one needs in college (not to mention the workplace) do not magically appear out of nowhere on one's 18th birthday or the day he shows up on campus; they need to be in place when he gets there. Or do we really want to send kids to college or out into the world thinking they can abstain from doing required work because a professor (or employer) "didn't make it fun?"
What happened to the idea that students come to school to study? That high school should be a place for serious intellectual inquiry and academic rigor? These are supposed to be institutions of learning, are they not? Are there no serious academics left among secondary-level educrats?
Those who believe that we should make high school more like elementary school and less like college are not serious people. They cannot truly be concerned with creating anything like a serious learning environment, let alone the long-term prospects of these kids. If our job is to prepare them for what lies ahead, then no purpose can be served by looking backward.