Prior research on the Measures of Academic Progress (MAP), a computer-adaptive test distributed by the Northwest Evaluation Association, has primarily focused on the Reading MAP for screening/benchmarking in elementary grades. The purpose of this study was to explore the functional form of growth and the extent to which student variability in growth was captured by the Mathematics MAP across a single school year using linear mixed-effects regression. Participants were 1608 middle school students from a school district in the Upper Midwest. Results supported a statistically significant nonlinear growth term for sixth grade and statistically significant, but small, monthly linear growth terms for sixth, seventh, and eighth grades. The Math MAP moderately captured individual variability across grades. Implications for research and practice are discussed.