![](https://cepa.stanford.edu/sites/default/files/ludgerw.jpg)
Professor of Economics, University of Munich; Director, Ifo Center for the Economics of Education
CERAS #513
Most studies find little to no effect of classroom computers on student achievement. We suggest that this null effect may combine positive effects of computer uses without equivalently effective traditional alternatives (such as looking up information) and negative effects of computer uses that substitute potentially more effective traditional practices (such as practicing skills). We confirm this hypothesis with data on different computer use activities in the international TIMSS test of math and science achievement. Our identification strategy exploits within-student between-subject variation in correlated random effects models that generalize student-fixed-effects models to subject-specific effects. Effects are mostly confined to developed countries.