Parents, educators, and politicians have long debated what students should learn in American schools--and how they should be taught.

Americans may get swept up in debates over education finance, school safety, and the latest classroom technology. But throughout the 20th century, their attention has never strayed far from what lies at the very heart of schooling: the curriculum.

What society chooses to fill children's minds with generates a degree of passion that few other issues in education can match.

So, too, does the matter of who decides what students should be taught. Here, the country has seen a historic shift. Teachers, administrators, and school board members still wield considerable clout, but, increasingly, state boards of education, legislators, and governors are exercising their prerogatives over subject matter and how it is taught.

The core curriculum of reading, writing, and arithmetic has long since been expanded to meet the changing demands of the nation. On the brink of a new century, educators continue to deliberate over what knowledge schoolchildren will need to conquer new challenges.

The fifth installment of "Lessons of a Century," a yearlong Education Week series of monthly special sections, looks at "The Evolving Curriculum."

Go to The Century Series, for a look at the series to date.