This study used hierarchical linear modeling to examine the relationship between an internet-based mathematics formative assessment and data from a mathematics summative assessment for primary grade learners (ages 5-7). Results showed a positive relationship between formative assessment data related to the concepts of counting and decomposing numbers and summative data. This relationship was more robust in classrooms where students demonstrated lower average performance on the formative assessment data. The results suggest that formative assessment can be more beneficial to encourage low achieving students in primary-grade mathematics classrooms. Therefore, we recommend teachers to use formative assessment practices more frequently in low achieved primary grade classrooms. The formative assessment process includes the cycle of data collection, data analysis, planning future instruction, and examining the impact of that instruction through cycling back to data collection. This study contributes to the field by providing more empirical data about the relationship between formative and summative assessment with primary grades' learners.