American high schools used to be the admiration of the world. But over the past several decades, other countries have outpaced us. In test scores. In college readiness. In workforce preparation. In student satisfaction and engagement. The list goes on.

Which leaves many of us asking, “How did we get here?”

The short answer is this: the public school system we know today was developed with all the best intentions and, for decades, a fair amount of success. At the turn of the 20th century, educational reformers such as industrialist Andrew Carnegie saw that our country needed a revolution in education to match the revolutions taking place in industry and society. In other words, they rethought school.

A uniform, standardized system based on time spent in school, in lessons—what came to be known as the “Carnegie Unit”—brought order and consistency to what had been a patchwork educational system. And it worked. But just because something worked well in the past doesn’t mean it will work well indefinitely.

Things changed. Industry changed. America and the world are in the middle of a new information revolution, and simply counting the hours of instruction we give our students and tracking them into college prep, general, or vocational strands will not work anymore. Instead of a guidepost, the rigidly standardized Carnegie Unit has become a straight-jacket for educators, schools, and most importantly, students.

We need students who know how to keep up with a massive growth of information, who are creative and critical thinkers, who can compete and thrive in a global economy. We need students who are ready to claim their future in a very unstandardized world.

If we free ourselves from the rigid framework of modeling education on time spent in the classroom—the Carnegie Unit approach—to adopting a design that prioritizes discovery, subject mastery, personalization, equity, and positive student relationships, what else do we free ourselves from? Would a classroom still necessarily consist of a blackboard, a teacher’s desk, and thirty or so seats? Or could the classroom be a laboratory, a museum, a trek into nature, an internship? Would all schools look like carbon copies of one another—in a community but somehow separated from it? Would the day be divided into periods by factory-like bells? Would teachers “teach to the middle”—a one-size-fits-most approach—or would they be empowered to teach to each and every individual?

When we start to challenge old education assumptions, the Carnegie Unit chief among them, the most pertinent question stops being, “How did we get here?” and becomes, “Where are we going next?”