Gauging the knowledge students acquired was an endeavor of educators long before the 20th century dawned, but it has become a national obsession as the century ends.

In the 19th century, teachers relied on recitations and, later, written examinations to plumb the depths of their charges' knowledge. Shortly into this century, though, testing experts devised new breeds of assessments--designed to calculate intelligence and to measure achievement in a standardized fashion.

The objectivity and speed with which the new tests could be scored made them a popular commodity. Soon, multiple-choice and true-false questions displaced the written examination. Critics, however, contended that the results inaccurately reflected student ability, particularly for girls and members of racial and ethnic minorities.

Over the decades, administrators often used IQ tests to track students by ability and standardized achievement tests to evaluate students' mastery of the curriculum.

Despite the significance of such assessments within the education community, policymakers had long ignored standardized tests. But by the 1970s, state and federal officials began wielding them as tools to judge how well schools did their jobs. Today, students are finding the stakes attached to tests are rising for them as well.

The sixth installment of "Lessons of a Century," a yearlong Education Week series of monthly special sections, looks at "The Assessment Culture."

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