Carnegie Unit

The Carnegie Unit and the Student Hour are strictly time-based references for measuring educational attainment used by American universities and colleges; the Carnegie Unit assesses secondary school attainment, and the Student Hour, derived from the Carnegie Unit, assesses collegiate attainment.

Per its original definition, the Carnegie Unit is 120 hours of class or contact time with an instructor over the course of a year at the secondary (American high school) level. Strictly speaking, this breaks down into a single one-hour meeting, on each of five days per week for a total of 24 weeks per year. However, knowing that classes usually meet for 50 minutes yields a value of 30 weeks per year. However, further complicating the computation is the fact that American schools typically meet 180 days, or 36 academic weeks, a year. A semester (one-half of a full year) earns 1/2 a Carnegie Unit.

The Student Hour is approximately 12 hours of class or contact time, approximately 1/10 of the Carnegie Unit (as explained below). As it is used today, a Student Hour is the equivalent of one hour (50 minutes) of lecture time for a single student per week over the course of a semester, usually 14 to 16 weeks.

These units came about, during the late 19th and early 20th centuries, through a series of three disjointed events, all designed to standardize the collegiate educational experience.

Prior to this time (late 19th century) admission to post-secondary education involved comprehensive examination, either by public oral process, or private written process. These processes varied greatly among U.S. colleges and universities, due to the highly subjective nature of these types of examination. Eventually, these methods were slowly discredited due to their poor reliability and validity.

Charles W. Eliot at Harvard University, in the late 19th century, devised both a contact-hour standard for secondary education, and the original credit-hour collegiate post-secondary standard. In 1894, the National Education Association endorsed the standardization of secondary education.

Widespread adoption of the 120-hour secondary standard did not occur until the Carnegie Foundation (established in 1906) began to provide retirement pensions (now known as TIAA-CREF) for university professors with the qualification that universities must enforce the 120-hour secondary standard. By 1910, nearly all secondary institutions in the United States used the "Carnegie Unit" as a measure of secondary course work.

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