College & Workforce Readiness What the Research Says

The High School Credit-Hour: A Timeline of the Carnegie Unit

By Sarah D. Sparks — December 15, 2022 4 min read
Shadows of Walla Walla (Wash.) High School seniors waiting to enter graduation are cast on a school wall.
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The credit-hour, often known as the Carnegie unit, has been the essential measure of American secondary and higher education for more than a century.

Now the Carnegie Foundation for the Advancement of Teaching, which developed the time-based system in 1906, wants to consign it to history. The foundation has just launched what foundation President Tim Knowles expects to be a decade-long research, practice, and legislative initiative to replace time as the essential measure of learning.

That would be a major change for a measurement unit that has become so firmly embedded in the nation’s education system, although not without some long-running criticism.

Here are some key points in time in the evolution of the time-based credit system.


Industrialist Andrew Carnegie donates $10 million (more than $304 million in today’s money) to create a retirement pension fund for teachers in colleges, universities, and technical schools (which became TIAA-CREF). Trustees from the newly created Carnegie Foundation for the Advancement of Teaching realize that there are no standards to distinguish high schools and various types of postsecondary institutions.

Andrew Carnegie, founder of the Carnegie Steel Company, in his study in New York.


In the journal Science, the foundation proposes the need for a new metric to define education. Ultimately, the Carnegie unit measures the amount of time a student studies a subject with a teacher. One “student hour” could include “lecture, lab work, or recitation room work, for a single pupil.” One hundred twenty hours equal one “credit.” Fourteen credits are the minimum for four years of high school preparation. The foundation agrees to back teacher pensions for any postsecondary institution that follows a 120-hour credit standard.


Engineer Morris Llewellyn Cooke, releases the 133-page report, “Academic and Industrial Efficiency,” linking education standards to the then-popular “scientific management” movement he helped promote. Scientific management, launched by fellow engineer Frederick Taylor, aimed to analyze and measure work processes to improve labor efficiency, originally in factories. Cooke’s report advised universities to adopt Carnegie’s “student hour,” with each course credit representing three student-hours a week for 16 weeks. He proposed the system be used to calculate building and staff expenses for university budgets.


Sydney Besvinick, a University of Miami professor, publishes a critique of the Carnegie unit in the magazine Phi Delta Kappan, arguing it is being used as a measure of the quality of learning, when it was designed only as a measure of a student’s exposure to content.


The federal Higher Education Act significantly increased federal financial aid, using student-hours as a measure of programs.

U.S. President Lyndon B. Johnson, seated at the desk he used while a student secretary at Southwest Texas State College 35 years ago, signs the Higher Education Act at San Marcos, Texas, Nov. 8, 1965. Looking over the president's shoulder is Lady Bird Johnson and to her right are, Mrs. Jake Pickle; Rep. James Jarrell "Jake" Pickle, D-Texas; J.C. Kellam, of Austin, partially hidden; and James H. McCrocklin, president of the college. The men at extreme left are not identified.


The Florida Commission on Education Reform and Accountability’s “Blueprint 2000,” is one of several critiques of the time-based credit system among states and think tanks in the 1990s. It argues that time-based credits focus on labels of classes rather than measures of what students know and can do in each subject.


U.S. Secretary of Education Margaret Spellings launches the Commission on the Future of Higher Education, which urges higher education institutions to collect individual student data and report measures of “meaningful student learning outcomes,” not just seat time.

U.S. Secretary of Education Margaret Spellings speaks to a luncheon held to address the future of New Jersey's high schools, sponsored by the group New Jersey United for Higher Education on Wednesday, Feb. 22, 2006 at Fairleigh Dickinson University in Madison, N.J.


Global ministers of education meet in Athens under the auspices of the Organization for International Cooperation and Development, which administers the Program for International Student Assessment, to discuss the need for more comprehensive measures of learning in high school and higher education. The group begins work on a project to compare practices by multiple countries.


As part of revisions to federal financial aid program regulations, the U.S. Department of Education attempts to create a national definition for the student-hour. The proposal sparks sharp criticism, including a letter signed by more than 70 higher education groups, who argue it conflates seat time and learning outcomes.


The New America Foundation releases a report arguing that time-based credit has become less useful for the rising number of students taking online classes and attending college part-time. The Bill & Melinda Gates Foundation dedicates funding to explore mastery-based and other non-time-based credit systems, and states like New Hampshire begin piloting mastery systems.


In his announcement of the federal High School Redesign Initiative, Education Secretary Arne Duncan calls for high school credit to be “defined by learning outcomes, not ‘seat time’ requirements.”

President Barack Obama and Education Secretary Arne Duncan visit a classroom at the Pathways in Technology Early College High School (P-TECH) in Brooklyn, New York, Oct. 25, 2013.


After two years of work by a national task force, the Carnegie Foundation for the Advancement of Teaching publishes a report on time-based credit, defending the use of the Carnegie unit and student-hour as problematic, but the best broadly available measure of student learning.

121522 Carnegie Unit BS


As the COVID-19 pandemic prompts long-term, widespread closures across schools and universities, the majority of states waive or add flexibility to the credits required for high school graduation and the seat time needed to complete them. As the pandemic continues, some states extend this flexibility and look for more ways to expand non-time-based credit systems.


Tim Knowles, the 10th president of the Carnegie Foundation for the Advancement of Teaching, announces an initiative to replace the Carnegie unit, saying: “It seems past time to think about how do you build a legitimately outcomes-based system where learning can happen anywhere.”

Sources: The Carnegie Unit: A Century-Old Standard in a Changing Education Landscape; “Cracking the Credit Hour"; Education Week and other news reports


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