NCPA - National Center for Policy Analysis


August 24, 2007

Although people generally agree that teacher quality affects student achievement, there is much less agreement on how to measure teacher quality. Given the long held belief that more education produces better teachers, many American school districts pay teachers with master's degrees substantially more, even though a number of studies suggest that having a master's degree has little if any effect on student achievement.

In a new report from the National Bureau of Economic Research, co-authors Charles Clotfelter, Helen Ladd and Jacob Vigdor study the effect of teacher credentialing on student achievement using data on 75 percent of all children in North Carolina in grades 3, 4, and 5 from 1994 to 2003.  Their results show that having a graduate degree has little effect on student achievement:

  • Teachers who entered teaching with a master's degree, or who earned it within five years of beginning to teach, were as effective as teachers without a master's degree.
  • Teachers who earned a master's degree more than five years after they started teaching were less effective than those without master's degrees.

As in previous studies, the authors find here that teachers with more experience are better teachers. This is the case even after accounting for the fact that the teachers who remain teachers may, on average, be less effective than those who leave:

  • The benefit of experience peaks at 21-27 years of teaching and adds 0.092 to 0.119 standard deviations to student achievement scores.
  • More than half of that gain occurs during the first years of teaching.
  • Teachers who come from competitive undergraduate institutions are somewhat more effective than those who come from uncompetitive colleges or universities, the researchers find.

Source: Linda Gorman, "Teacher Credentials Don't Matter for Student Achievement," NBER Digest, August 2007; based upon: Charles Clotfelter, Helen Ladd and Jacob Vigdor, "How and Why Do Teacher Credentials Matter for Student Achievement?" National Bureau of Economic Research, Working Paper No. 12828, January 2007. 

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