The number of students ages 6 to 21 enrolled in special education rose in the most recent year for which the federal government has data, driven by increases in the number of students classified as having autism or "other health impairments." It was the fourth year in a row for such an increase. In fall 2015, about 5.9 million students enrolled in the 50 states, the District of Columbia, and Bureau of Indian Education Schools received services through the Individuals with Disabilities Education Act.