IDEA was originally enacted by Congress in 1975 to ensure that children with disabilities have the opportunity to receive a free appropriate public education, just like other children. The law has been revised many times over the years.
The most recent amendments were passed by Congress in December 2004, with final regulations published in August 2006 (Part B for school-aged children) and in September 2011 (Part C, for babies and toddlers). So, in one sense, the law is very new, even as it has a long, detailed, and powerful history.