The present study evaluated the psychometric properties of the Early Literacy and Numeracy Observation Tool (ELNOT), a tool aimed at identifying children who are at-risk or gifted, and monitoring children's academic progress. Kindergarteners (N = 356; 173 junior kindergarteners) were assessed at two time points (fall and spring). ELNOT consists of four literacy and six numeracy tasks; some tasks were eliminated from the analyses due to floor or ceiling effects. The measurement precision of three tasks (Print Concepts, Letter Identification, Number Recognition) was examined through item analyses. Overall, these tasks demonstrated sufficient measurement precision for most junior kindergarteners and some senior kindergarteners. The measurement invariance of five tasks (Print Concepts, Letter Identification, Early Spelling, Number Naming, Magnitude Comparison) was examined across gender, kindergarten level, and time through multiple-group confirmatory factor analyses; the model structure was invariant across all comparisons. ELNOT can accurately identify junior kindergarteners who are potentially at-risk.