Scale-score reporting is a recent innovation in the National Assessment of Educational Progress (NAEP). With scaling methods, the performance of a sample of students in a subject area or subarea can be summarized on a single scale even when different students have been administered different exercises. This article presents an overview of the scaling methodologies employed in the analyses of NAEP surveys beginning with 1984. The first section discusses the perspective on scaling from which the procedures were conceived and applied. The plausible values methodology developed for use in NAEP scale-score analyses is then described, in the contexts of item response theory and average response method scaling. The concluding section lists milestones in the evolution of the plausible values approach in NAEP and directions for further improvement.