Using State Longitudinal Data Systems for Education Policy Research : The NC Experience. Helen F. Ladd CALDER and Duke University Caldercenter.org [email protected] Examples of research in NC by CALDER researchers. Charter schools (Bifulco and Ladd)
Helen F. Ladd
CALDER and Duke University
Race, gender, free lunch status, LEP
Good match – 75 percent
A student’s achievement in year t is a function of:
(accounts for the cumulative nature of achievement)
(e.g. class size, profile of students in the class)
(e.g. race, gender, poverty status)
No fixed effects
With school fixed effects
2. Levels. Better, but problem of sorting within schools remains and potential bias from lagged achievement; direction of bias unclear (see our JHR paper)
3. Gains. Downward bias from misspecified persistence effect.
Full use of the longitudinal aspect of the data
With student fixed effects
4.Levels (but no lagged achievement). Lower bound estimates of effects of teacher credentials
5. Gains. Upward bound estimates of effects of teacher credentials
All test scores are normalized to have a mean of 0 and a standard deviation of 1.
=> coefficients of interest will be small. E.g. 0.05
Point of reference .
Compare test score of a typical student whose parent has a high school degree but no college degree to the test score of a student whose parents are college educated.
Estimated effect size = -0.11
Question : are the effects of teacher credentials on student achievement large enough to counter this negative effect of relatively low parental education?
(Base = noncompetitive)
Other license -0.059
(Base = regular license)
(Note: all coefficients are statistically significant)
MA before teaching -0.009
MA 1-5 years into teaching -0.005
MA 5+ years into teaching -0.010*
* indicates that the coefficient is statistically significant at the 0.05 level.
Comparison of teacher with average/strong credentials compared to one with weak credentials
math + 0.15 to 0.20
reading +0.08 to 0.12
And more – to come. Stay tuned and check the CALDER web page later this summer.