Transcript Teacher Credentials and Student Achievement in High
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.