This study identified student characteristics associated with school year mobility for more than 260,000 students in grades 4 through 8 who began the 2016-17 school year at a school in one of ten Houston area school districts. Of these students, 20,154, or just under 8%, changed schools at least once during the school year. Three characteristics stood out in predicting whether a student changed schools. First, Black students were more likely to be mobile during the year than students from other race/ethnicity groups, but a portion of these differences were explained by other characteristics. Second, students with lower STAAR scores in the prior school year were more likely to change schools than their peers with higher STAAR scores. Finally, prior mobility predicted future mobility as students who changed schools in the previous school year were more likely to be mobile again than their non-previously mobile peers.