It looks to me as if one of the most acclaimed reforms of today’s education profession—not just in the U.S. but also all over the planet—is one of the least examined in terms of actual implementation and effectiveness. How often and how well do instructors, whose administrators and gurus revere the concept of differentiated instruction, actually carry it out? How well does it work and for which kids under what circumstances? So far as I can tell, nobody really knows.

I’ve been roaming the globe in search of effective strategies for educating high-ability youngsters, particularly kids from disadvantaged circumstances who rarely have parents with the knowledge and means to steer them through the education maze and obtain the kind of schooling (and/or supplementation or acceleration) that will make the most of their above-average capacity to learn.

As expected, I’ve found a wide array of programs and policies intended for “gifted education,” “talent development,” and so forth, each with pluses and minuses.

But almost everywhere, I’ve also encountered some version of this assertion: “We don’t really need to provide special programs, classrooms, or schools for gifted children because we expect every school and teacher to differentiate their instruction so as to meet the unique educational needs of all children within an inclusive, heterogeneous classroom.”

A thoroughly laudable goal, say I, but how realistic is it? How well is it being done? And does it really meet their needs, or is it ultimately a politically acceptable excuse for not doing anything special for high-ability children?

The concept of differentiated instruction seems to arise from five roots:

“Brain research” that has (not always with the finest of scientific rigor) claimed to identify diverse “learning styles” and forms of “intelligence,” thereby challenging teachers to individualize their classroom practice to accommodate such student variability. The desire of many in the special-ed world—parents and experts alike—to “mainstream” disabled children in regular classrooms to the greatest extent possible, thereby challenging teachers to accommodate and adapt their instruction to meet the needs of these youngsters, too. The push for uniform statewide (and now multi-state) academic standards that, it is claimed, will cause every child to become “proficient” (in NCLB lingo) or “college and career ready” (in today’s preferred terminology). An array of ideological and budgetary considerations that reject tracking, ability grouping, “pull-out” programs, and other forms of educational separation (often including both acceleration and grade repetition) on grounds that such practices are morally wrong, socially and educationally undesirable, politically imprudent, and just plain unaffordable. Growing interest in “blended learning” and other classroom uses of technology, which help teachers customize and individualize learning by letting some students move at their own pace online while teaching other kids in smaller, perhaps more homogeneous groups.

In response, “regular” teachers are tasked with customizing, tailoring, and individualizing their instruction so that administrators and policy types can declare with straight faces that their classrooms are diverse and inclusive and that every child’s singular education needs are being satisfactorily met.

To equip teachers with such remarkable pedagogical prowess, all manner of courses, books, in-service programs, itinerant experts, and summer workshops are available. (Google “differentiated instruction” and “professional development” together and you will get half a million hits.) Organizations such as the ASCD devote much energy to promoting this approach to education.

In short, it’s quite a big deal.

Unless, it appears, you are actually the teacher of a heterogeneous class that contains children with many different needs, different levels of prior achievement, and different “learning speeds,” at least in whatever subjects you are responsible for teaching them. That teacher, it appears to me, is being given an all-but-impossible assignment, akin to presenting a general-practitioner physician with twenty-three patients who manifest different symptoms, differing degrees of illness, and, upon examination, very different ailments. Some might benefit more from an oncologist, an orthopedist, a cardiologist, or perhaps a dietitian, personal trainer, or podiatrist. It’s unlikely that any given doc will do an outstanding job with all of them. Indeed, the most valuable thing he could do for many would be to refer them to the appropriate specialists.

Much the same can be said about attorneys. The guy who drafts your will is probably not best suited to get you a divorce or defend you in a larceny trial.

But teachers are expected to be all things to (almost) all youngsters. And most of those I talk to about this mandate acknowledge that, while technology and small classes surely help, they do not feel like they’re differentiating all that well.

Some, of course, manage better than others, and some “inclusive” classrooms aren’t so very diverse. The tendency of many, however—this is evident when I observe classes—is to respond to the mandate in either (or possibly both) of two ways: They may engage in some form of “ability grouping” within the classroom—which may well be what teachers “hear” when someone says “differentiate,” though it’s surely not what the gurus of the field intend. Or, if they stick with full-class instruction, they pitch much of their instruction to kids in the middle 60 percent or so of the achievement/ability/motivation distribution, doing less for pupils who are either lagging far behind or surging ahead. But when policy intervenes to reshape the teacher’s priorities, it is invariably on behalf of the laggards, for they are the beneficiaries of major governmental efforts—such as NCLB and IDEA—to advance the education of youngsters who face difficulties and to reward schools and teachers that accomplish this.

By contrast, in my experience, pretty much the only pressure on teachers to attend to the learning of their quicker, higher-achieving pupils comes from parents—and the pressure-exerting parents are almost always ensconced securely in the middle class.

Worse, high-ability children from disadvantaged circumstances typically attend schools with many other disadvantaged youngsters. The real pressures on such schools and their staffs are to meet student needs that are often ubiquitous and acute in such communities (e.g., health, nutrition, remediation, attendance, language, discipline) rather than to maximize the learning of their high achievers. And, indeed, there’s research evidence that a school’s priorities do tend to align with its most pressing and widespread student needs.

Plenty of teachers strive to do right by all their pupils. But I’ve sat in classrooms and watched as “smart” kids twiddled their thumbs (or acted out) in boredom and frustration while the instructor toiled to get basic concepts into the heads of those who, for whatever reason, were finding it much harder to learn. And when speaking to audiences of teachers, I’ve noted that any suggestion that “differentiated instruction” works better in theory than in reality usually elicits applause or, at minimum, a knowing and somewhat cynical chuckle.

Veteran “gifted educators” whom I respect say things like this: “Many gifted children’s needs can be met in the regular classroom, if grouped with academic peers for part of the day and if under the reign of a very gifted teacher. The likelihood of getting a very gifted teacher is, however, too small.” And, “Talent development happens through an acceleration of a curriculum. Differentiation doesn't typically address the needs of very highly able children.”

Perhaps it can—and there are schools and classrooms that try hard. Yet when a colleague of mine visited one Maryland school that puts meticulous differentiation high among its priorities, he reported back that these arrangements look awfully “rickety, held with lots of duct tape and chewing gum, and subject to collapse without just the right staff and parent support.” (And that’s at the elementary level; all of this grows vastly harder in the upper grades.)

Can this reliance on individual teachers to meet all pupils’ needs possibly be robust enough to bear the enormous policy and professorial weight that’s being placed on it today, particularly for high-ability pupils? Does anybody really know? The research literature appears distressingly thin. So let me invite proponents of differentiated instruction to supply evidence that this strategy is effective, particularly for educating children of high ability, versus approaches that entail separation, augmentation, or acceleration. And, while they’re at it, please also offer data, research, and evaluation evidence that speak to the sorts of questions I posed at the outset: How well is differentiated instruction carried out and by how many teachers? How well does it actually work and for which kids under what circumstances? I’d really like to know, and so, I am sure, would many others.