Part C of the IDEA requires that infants and toddlers with disabilities receive early intervention services from birth through age 3. These services are provided according to an Individualized Family Service Plan (IFSP. In contrast, Part B of the IDEA requires that children with disabilities, from age 3 to 21, are provided a free appropriate public education.
Department of Education Regulations
In addition to the Federal law, the U.S. Department of Education publishes regulations that clarifies what the law means. States may add more provisions to further regulate how schools provide services, but they cannot reverse any provision specifically included in the federal statute.