The primary charge of special educators is to provide eligible students with disabilities a special education that confers a free appropriate public education (FAPE). The U.S. Supreme has held that a FAPE consists of two types of student rights: Procedural and substantive. Because a student's IEP is the blueprint of a his or her FAPE, a student's IEP team must ensure that the IEP process and document is both procedurally correct and substantively meaningful. In this article we address the most serious substantive errors that teams make when developing students' IEPs. It is critically important that special educators understand the nature of substantive errors and avoid making them when developing students' IEPs.