Above-level testing is the practice of administering aptitude or academic achievement tests that are designed for typical students in higher grades or older age-groups to gifted or high-achieving students. Although widely accepted in gifted education, above-level testing has not been subject to careful psychometric scrutiny. In this study, I examine reliability data, growth trajectories, distributions, and group differences of above-level test scores obtained from the Iowa Tests of Basic Skills and Iowa Tests of Educational Development. Two hundred twenty-four middle school students participated in this study. All participants were tested at least 1 time for an overall total of 435 times. Longitudinal analyses was performed with hierarchical linear modeling and indicated that substantial differences exist between students from overrepresented ethnicities (White and Asian Americans) and those from underrepresented ethnicities (Hispanic and African Americans) in both initial scores and the rate of score gains. Sex differences existed only for the rate of score increases for above-level reading scores. Socioeconomic differences existed but did not have a unique impact beyond that of the ethnicity variable. A discussion of these results within a wider gifted education context and suggestions for further research are included.