Students' prior achievements in school have significant correlations with their later achievements. Specifically, students' prior numeracy achievement is the most important predictor of later numeracy success. However, the assessment of this predictor across gender and its trend across students' year levels is often overlooked or not adequately investigated. This study examined the relationships between prior numeracy achievement and its influence on students' later numeracy achievement across gender. A focus on students' year level also supported this examination. The data source was the Australian National Assessment Program--Literacy and Numeracy (NAPLAN) numeracy results of Years 5, 7 and 9 students (ages 9 to 14) from the 2017 to 2021 test years. The NAPLAN numeracy scores were analysed using regression analysis. The author examined prior numeracy achievement to determine the predictive value for students' numeracy performance in NAPLAN across students' year levels and gender. Findings from this study indicate that prior NAPLAN numeracy results for students were found to be very large in its predictive value (between R[superscript 2] = 0.591 and 0.747) across the year levels. Notably, the predictive value showed an increasing pattern as students progressed through their academic years. Additionally, the study observed a discernible influence of gender on the predictive value of prior numeracy results. Potential initiatives to assist the educational outcomes of students across gender are discussed. Awareness of the influence of numeracy performance across gender might help teachers and educators create better and more efficient mathematics programs and targeted interventions. Such a decision requires identifying the relevant factors and measuring their degree of influence across students' year levels and gender.