This study examined the unique and combined associations of homelessness and school mobility with educational well-being indicators, as well as the mediating effect of absenteeism, for an entire cohort of third-grade students in Philadelphia. Using integrated archival administrative data from the public school district and the municipal Office of Supportive Housing, multilevel linear models were estimated to test these associations while adjusting for nesting of students within schools. Findings demonstrated that homelessness had a unique association with problems in classroom engagement, school mobility was uniquely related to both academic achievement and problems in classroom engagement, and experiencing both homelessness and school mobility was the most detrimental for both forms of educational well-being. Absenteeism was found to partially mediate the relations between homelessness, school mobility, and problems in task engagement. Results provide support for the McKinney-Vento Homeless Assistance Act and the need for educational policies for mobile children. (Contains 5 tables.)