This chapter discusses the dimensions of special education that make it—or, at least should make it special. It presents the observation that special education's bottom line should be effective instruction of learners at the extremes of statistical distributions of educationally relevant characteristics. The most salient characteristic of special education is individualized instruction. Without individualization, special education simply doesn't exist. Individualization of instruction is demanded by the wide range of types and levels of severity of disabilities and types and levels of gifts and talents. Special education is a way of addressing the core problem of variation in achievement and ability in the group of children to be taught. Special education exists for the primary purpose of providing better instruction to students at the extremes of statistical distributions of school achievement. Assessment, placement, and every other aspect of special education must serve the primary purpose of better instruction of exceptional students.