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. –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

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.

Approach We use test scores on five tests typically taken by 9 th or 10 th 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 10 th grade in 1999/2000; 2000/01; 2001/02; 2002/03 Concern about selection into courses

Models Preferred model. Student a chievement 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.

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 : s.d. (From alternative model)

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

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

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

Magnitudes Predicted achievement difference for teacher at the 90 th percentile compared to a teacher at the 10 th percentile of the predicted achievement distribution standard deviations Large effect Relative to class size reduction of 5 students – 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.

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

Across classrooms – algebra I Novice teacher (%) Lateral entrant (%) Teacher test score <1 sd Blacks Whites

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 => Maldistribution of teachers contributes to black- white achievement gap.

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.