Repeated measurements of student ability (i.e., progressing monitoring) is an essential element of informed decision-making when adjusting instruction. An important characteristic of progress monitoring measures is frequent administration to identify areas of concern and to evaluate academic growth. The purpose of this study was to determine if STAR Math is sensitive to small incremental growth across a semester. Within two southern school districts, 114 fifth grade students' progress monitoring data were collected weekly, and a latent growth curve was used to estimate students' change in math ability. Results indicated STAR Math is sensitive to small incremental growth, with a statistically significant and positive slope, suggesting students using STAR Math showed improvement in ability over the semester.