Abstract. Differences in reading, mathematics, and writing achievement of Grade 7 students as a function of mobility were examined with and without controls for economic status in this investigation. Data were obtained from the Texas Education Agency Public Education Information Management System for the 2002-2003 through the 2007-2008 school years. Statistically significant differences were revealed in reading, mathematics, and writing test scores as a function of student mobility, both when controlling for and not controlling for economic status. Mobile students had statistically significantly lower reading, mathematics, and writing test scores than did non-mobile students for all 6 school years. Implications for policy and practice and suggestions for future research were made.