This paper relates frequency of interstate migration and the likelihood of a child's being enrolled in school at the modal grade for age, controlling for socioeconomic status of the family. The 1970 Census of Population obtained information on school enrollment and current grade, state of birth, residence in 1965, and residence in 1970. A measure of relative progress in school was obtained by adjusting a child's age back to October 1, 1969 and comparing with grade of enrollment. The probability of a child's being enrolled below the modal grade for age is highly correlated with the various measures of socioeconomic status and family stability. This measure of relative progress in school was cross-tabulated with frequency of interstate migration. This indicator understates the actual amount of interstate migration, for some children could have moved several times between birth and 1965 and between 1965 and 1970, but in each case only one move would have been counted. Frequent interstate migration is found to be associated with an increased likelihood of being enrolled below the modal grade for age among children whose parents are not college graduates. For children of college graduates frequent interstate migration is associated with a reduction of grade skipping. Interstate migration is most likely to be undertaken by well-educated persons whose children tend to do well in school, and for this reason children who have made frequent interstate moves are less likely to be behind in school than less mobile children. (Author/JM)