Researchers intending to identify the unique characteristics of dyscalculia rely upon the problematic and imprecise proxy of low mathematics achievement. Although detailed case studies of adults with dyscalculia have offered insight into its characteristics, we do not yet know if these characteristics are unique to dyscalculia and could be used to screen younger students for these understandings. To address this, we designed a group-administered written assessment based on the unconventional understandings found in adults with dyscalculia to investigate whether these understandings are atypical. In study 1, we assessed 390 grade 6-8 students to investigate the prevalence of these understandings. In study 2, we assessed 80 grade 6-8 students and recruited three students who demonstrated high levels of unconventional understandings. We collected additional assessment data and determined that all three students met stringent clinical dyscalculia criteria. These studies provide a proof-of-concept for designing dyscalculia screeners based on the characteristics identified in adults with dyscalculia.