This article examines late nineteenth-century preadmission records taken at the Pennsylvania Training School in order to better understand the biographical and medical characteristics of persons seeking admission to this prominent school for the “feeble-minded.” It draws on those records to then explore how guardians and the superintendent assessed the likelihood and nature of educational improvement. A pioneering institution for the education of people with intellectual disability, the Training School, generally known as “Elwyn,” kept extensive biographical and etiological records that contain a previously untapped wealth of data. These records offer valuable insight into parents’ understanding of their children's disability, their hopes for improvement, and opinions of what would constitute a successful, productive life. The authors use the records to develop a statistical profile of the characteristics of applicants that superintendent Dr. Martin Barr would deem most likely to improve from instruction, and a similar profile for those deemed incapable of improvement. We situate our analysis of the records within the Gilded Age context of anxieties surrounding the state of public education and worker productivity in an industrial economy. In the field of disability studies, the article adds to our understanding of how superintendents constructed and applied the “medical model” of disability and its tension with the lived social experience of disability.