About 13 percent of children aged 3 through 21 enrolled in public schools received special education services in school year 2015-16, and about 3 percent of children from birth through age 2 received special education services. Concerns about the difficulties identifying and evaluating children for special education have been raised by the media, experts, and special education advocates. GAO was asked to examine how states implement Child Find and how Education monitors it. This report examines (1) factors that may account for differences in the percentage of children receiving special education services across states, and (2) how Education and selected states monitor and support Child Find efforts. GAO reviewed federal special education data, agency documentation, federal laws and regulations, and selected state laws; and interviewed Education officials, officials from four state agencies and 15 school districts in those states (Colorado, Iowa, Massachusetts, and New York), and representatives of organizations that advocate for families of individuals with disabilities as well as special education subject matter specialists.