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 : -0.116 s.d.

(From alternative model)

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

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.

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)

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 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.

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 % Lic.test score –0.057

13.3 % 0.117

Across classrooms – algebra I

Blacks Novice teacher (%) 20.24

Lateral entrant (%) 7.23

Teacher test score <1 sd 8.27

Whites 16.75

4.02

3.80

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.

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.