TY  - JOUR
AU  - Hoxby,Caroline M.
TI  - The Effects of Class Size and Composition on Student Achievement:  New  Evidence from Natural Population Variation
JF  - National Bureau of Economic Research Working Paper Series
VL  - No. 6869
PY  - 1998
Y2  - December 1998
UR  - http://www.nber.org/papers/w6869
L1  - http://www.nber.org/papers/w6869.pdf
N1  - Author contact info:
Caroline M. Hoxby
Department of Economics
Stanford University
Landau Building, 579 Serra Mall
Stanford, CA 94305
Tel: 650-725-8719
Fax: 650-725-5702
E-Mail: choxby@stanford.edu
AB  - I use natural population variation to identify the effects of class size and composition on student achievement.  I isolate the credibly random component of population variation in each grade and school district and use this component to generate instrumental variables for class size and composition.  I also exploit the discontinuous changes in class size that occur when natural population variation triggers a change in the number of classes in a grade in a school.  Discontinuity-based results are both consistent and precise only when applied to within-district changes in class size and population.  I find that reductions in class size from a base of 15 to 30 students have no effect on student achievement.  The estimates are precise enough to identify improvements in math, reading, or writing achievement of just 3/100ths of a standard deviation.  I find that the presence of black students in a class, in an of itself, has no effect on achievement.  I demonstrate that estimates of the effect of racial composition that rely on between-district comparisons suffer from substantial bias.  Finally, I show that more female classes perform significantly better in writing in the 4th through 8th grades and in math in the 4th grade.  Comparison of the effects to average male-female differences in test scores suggest that gender composition alters classroom conduct.
ER  -