What is the I.D.E.A. Law for Students with Disabilities?

What is the IDEA federal law for students with disabilities?
According to the US Department of Education website, “The Individuals with Disabilities Education Act (IDEA) is a law ensuring services to children with disabilities throughout the nation. IDEA governs how states and public agencies provide early intervention, special education and related services to more than 6.5 million eligible infants, toddlers, children and youth with disabilities. Infants and toddlers with disabilities (birth-2) and their families receive early intervention services under IDEA Part C. Children and youth (ages 3-21) receive special education and related services under IDEA Part B.”
There are 13 categories of exceptionality that make children eligible to receive IEP (Individualized Education Program) services using IDEA funding. These special education categories include: autism, deaf-blindness, developmental delay, emotional disturbance, hearing impairment (including deafness), mental retardation, multiple disabilities, orthopedic impairment, other health impairment, specific learning disability, speech or language impairment, traumatic brain injury, visual impairment.
IDEA means a child qualifies for having a disability in one of the above categories. In order for a child to ‘qualify’ for special education services they must go through the evaluation process.