A head-scratching puzzle of school reform over the past century is the innovation that arrives in tinsel and enters tax-supported public schools. Often districts adopt such glittering new programs and they settle into protected niches. But, and here is the puzzle, praised and admired as they are, they cannot break out of that nook. They stick around at the edges of the system remaining isolated, failing to spread throughout the district.

Early 20th century Progressives had their Project Method and the Dalton Plan. Both were adopted in many public schools because they seemingly solved organizational, curricular, and instructional problems. And they had internal constituencies of teachers and administrators yet they remained on the periphery of school systems. They did not become standard practices across classrooms.

Mid-century curricular reformers had their New Math. Late-20th century insurgents rallied around Coalition of Essential Schools and Core Knowledgeprograms. And early 21st century reformers have their problem-based learningand International Baccalaureate programs still awaiting that magic moment when the “system” adopts the innovation district wide completely altering how teachers teach and students learn. All had supporters either inside or outside districts (or both) but failed to move from the margins to become regular programs across districts.

To many reformers, the difficulty of getting adopted into public schools appears to be the highest hurdle. It is not. School boards and superintendents adopt many new ideas and direct administrators to implement them as pilots or in particular classrooms.

The far larger hurdle is breaking out of the niche that the innovation occupies in the district. Out of 35 schools in a district, for example, a handful of teachers or one or two schools regularly use the innovation. Going district-wide remains a near impossible task.

Yet some organizational, instructional, and curricular innovations do break out of their niches and get adopted locally, state-wide, and even nationally. Consider the sponsoring of private kindergartens for poor children by middle-class women in the late-19th century and their steady growth in public schools to become established in nearly all elementary schools. Ditto for tax-supported pre-schools in the late-20th and early 21st centuries.

Or note the common classroom practice of grouping by performance and ability. Most early 20th century teachers taught the whole class as one whether there were 30 or 60 students. Beginning before World War I, however, Progressive teachers began to group students for reading. More and more elementary school teacher (far fewer secondary ones, however)) began dividing their students into groups for different activities. Such grouping practices spread to math and other elementary school subjects and has in time become established procedure.

Also early 20th century teachers had students memorize science passages in their textbooks and recite them to the teacher. The idea of students going outdoors to collect insects and life in streams slowly became part of the science curriculum during the 1920s and 1930s and such field trips are now embedded in the elementary and secondary school science curricula.

And since the mid-1990s, expanding access to computers–once relegated to a room with 30 devices in each school–now makes Internet-connected devices available to every single student.

So there have been successful scaling up of entry-level innovations to system-wide use. But these are the exceptions.

How, then, do I explain what appears to be a historical pattern of many adopted innovations occupying a niche in existing school systems yet they fail to spread throughout the larger system while other innovations slowly and steadily roll out to become incorporated across all public schools?

Disappointed promoters of their new programs blame teacher resistance or lack of expertise as the answer. Teachers are unprepared or inexpert in adopting new techniques and activities so they stick to ways that have worked for them day-in and day-out, ignoring the innovation.

Others point their fingers at principals and district office administrators who oppose the innovation on either ideological or financial grounds (or both). Sometimes, these administrators go further and point out the lack of research to justify system-wide adoption.

Then there are frustrated reformers who blame existing ways of governing and organizing public schools for the rejection of what appears to them as overwhelmingly successful programs. Rigid, bureaucratic rules block adopting innovations, they say. The century-old age-graded school with its “grammar of schooling” that great-grandparents, grandparents, and existing moms and dads have experienced stand in the way of progress, that is, their innovation. To boosters of the new program, these established ways of governing and organizing schools are taken for granted. They have become accepted by both professionals and parents as how schools were. And, more important, should remain.

While such explanations are often bandied about, I believe they only scratch the surface of a complicated puzzle. I speak not of those simple cut-out 15 interlocking pieces that kindergarteners play with but I mean one of those 1000-piece jigsaws. So how do I unravel this continuing conundrum of persistent and admired innovations –many producing prized student outcomes–occupying protected spaces in the organization yet still remaining isolated from the rest of the system?

The following posts on particular innovations—charter schools and Montessori programs–offer different ways of viewing this puzzle that is so thoroughly embedded in the history of U.S. tax-supported public schools yet too often unnoticed–save for a few researchers. Those researchers also suggest ways that such programs can move from the periphery to the center of schooling.