Objectives. We measured the impact of dental diseases on the academic performance of disadvantaged children by sociodemographic characteristics and access to care determinants Methods. We performed clinical dental examinations on 1495 disadvantaged elementary and high school students from Los Angeles County public schools. We matched data with academic achievement and attendance data provided by the school district and linked these to the child’s social determinants of oral health and the impact of oral health on the child’s school and the parents’ school or work absences. Results. Students with toothaches were almost 4 times more likely to have a low grade point average. About 11% of students with inaccessible needed dental care missed school compared with 4% of those with access. Per 100 elementary and high school–aged children, 58 and 80 school hours, respectively, are missed annually. Parents averaged 2.5 absent days from work or school per year because of their children’s dental problems. Conclusions. Oral health affects students’ academic performance. Studies are needed that unbundle the clinical, socioeconomic, and cultural challenges associated with this epidemic of dental disease in children. (Am J Public Health. 2012;102:1729–1734. doi:10.2105/AJPH.2011.300478)