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Charles T. Clotfelter Helen F. Ladd Jacob L. Vigdor

Teacher Credentials and Student Achievement in High School : A Cross Subject Analysis with Student Fixed Effects. Charles T. Clotfelter Helen F. Ladd Jacob L. Vigdor Presentation at CALDER Conference, Oct. 4, 2007. Motivation . Focus on teacher credentials.

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Charles T. Clotfelter Helen F. Ladd Jacob L. Vigdor

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  1. Teacher Credentials and Student Achievement in High School: A Cross Subject Analysis with Student Fixed Effects Charles T. Clotfelter Helen F. Ladd Jacob L. Vigdor Presentation at CALDER Conference, Oct. 4, 2007

  2. Motivation • Focus on teacher credentials. • Lively policy debate about whether teacher credentials are predictive of student achievement. • Credentials are potentially important policy levers. • Focus on high schools • Compare use of administrative data sets to examine teacher credentials in the elementary grades

  3. North Carolina data • End-of- course (EOC) tests in high schools. -- Preferable for this purpose to the comprehensive exit exams used in many states -- Based on standard course of study -- Scores count for 25 percent of a student’s grade in the course. => Teachers have strong incentive to teach the material and students to learn it. • Availability of data on a wide array of teacher credentials.

  4. Approach • We use test scores on five tests typically taken by 9th or 10th graders: English I, algebra I, biology, geometry, and ELP (economic, legal and political systems) • Four cohorts of students matched to their specific teachers Students in 10th grade in 1999/2000; 2000/01; 2001/02; 2002/03 • Concern about selection into courses

  5. Models • Preferred model. Student achievement in subject S = f(teacher credentials and characteristics, classroom characteristics, student fixed effects) Student fixed effects VIP. They control for all subject-invariant characteristics of students, such as basic ability or motivation. Equivalent to expressing everything relative to the mean for that student (Some remaining technical concerns, but see paper) • Alternative model. No student fixed effects; but include student level time-invariant characteristics, such as race and gender.

  6. Strategy • Basic model and many variations on each credential to examine in detail the achievement effects of credentials. • All test scores are normalized by subject and year to have mean of 0 and s.d. of 1. . • Magnitude – for purposes of comparison. Effects of being black with low SES : -0.116 s.d. (From alternative model)

  7. Credentials I • Teacher experience (base = no experience) 2-3 years 0.050 6-12 years 0.061[not diff. from 0.050] (With addition of teacher fixed effects, coefficients rise with experience) • Teacher licensure (base = regular license) Lateral entry -0.061 other -0.046

  8. Credentials II • Master’s degree (base= no grad. degree) Received after 5 years of teaching 0.009 Comparable results for NC elementary teachers - 0.010 in reading • National Board Certification (base = never certified) • Pre-certification 0.022 • Cert. app. year 0.048 • Has certification 0.051 (sig. dif from 0.022) Compare NC elementary results. No human capital effect.

  9. Credentials III • Teacher test scores (base= within 1 sd of average) < 1 sd below average -0.027 > 1 sd above average +0.010 (By subject – matters most for math courses) • Teacher certification (base =no certification) -- in subject 0.081 -- in related subject 0.074 -- in other subject 0.012 (not sig.) (Disaggregated. Biggest for math and biology)

  10. Magnitudes • Predicted achievement difference for teacher at the 90th percentile compared to a teacher at the 10th percentile of the predicted achievement distribution 0.183 standard deviations Large effect Relative to class size reduction of 5 students – 0.013 Relative to SES effects (from alternative model) –0.116 But, nonetheless, credentials explain only 1/5 to 1/3 of the overall variation in teacher quality.

  11. Distributional concerns Uneven distribution of teacher credentials across high poverty schools, defined by poverty quartile Q 1 (high) Q4 (low) Non reg. license 20. 5 % 13.3 % Lic.test score –0.057 0.117

  12. Across classrooms – algebra I

  13. Distributional effects • Consider black vs. white differences in teacher credentials in algebra 1 multiplied by estimated achievement effects. Across a large number of credentials – total adverse effect on black achievement = <0.02 • May seem tiny, but looms larger relative to the coefficient for a black student (controlling for other factors) of -0.057 => Maldistribution of teachers contributes to black-white achievement gap.

  14. Conclusions • Teacher credentials matter in high school • Aggregate effects are quite large • Some differences with findings at the elementary level. E.g. master’s degree; National Board Certification • Uneven distribution of teacher credentials across students by race contributes to the black-white achievement gap.

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