It is the dispute resolution procedure written into the Federal Sp Ed. law since 1975 passage of 94-142.
If you read a "Parents' Rights Booklet" from many states, it sound as tho' this would be a reasonable thing to do if you had a problem with your child's special education. Of the 627 people who responded to the survey I did last year on this site, only 23 had been to Due Process. It is difficult and stressful--can be expensive, and often does not produce the desired result even if you win. It's a very bad system and causes far more litigation than it prevents.
However, it is the process that every parent of a child with an IEP in the entire country is stuck with.
Sheila may be able to direct you to links that will explain it in detail. I'm sure there is something about it on www.wrightslaw.com
Quanya, sorry, I inadvertently edited your original post.
"...parents must disagree with the agency's evaluation and request the public agency to pay for an independent educational evaluation. 34 C.F.R. §300.502(b). This disagreement and request places the public agency on notice of the parents' intention to invoke their right to a publicly funded independent education evaluation. The public agency must then make an election. It can either acquiesce and pay for the independent educational evaluation or it must request a due process hearing to show that its evaluation is appropriate. Except for this criteria, the public agency is expressly prohibited from imposing conditions or timelines related to obtaining independent educational evaluations at public expense. "