Purpose: The purpose of this paper was to investigate the influences of calendar year, year level, gender and language background other than English (LBOTE) on student achievement in literacy and numeracy relative to class size. Design/methodology/approach: Data for this study were collected over five years (2008-2012) as test results from the Australian National Assessment Plan in Literacy and Numeracy (NAPLAN) in Years 3 and 5 from over 100 Sydney primary schools. Findings: It was found that the most important factors influencing academic performance in literacy and numeracy were, in descending order: gender, LBOTE, the calendar year in which the test was conducted, followed by class size. All variables were significantly associated with NAPLAN performance, but effect size estimates for class size were close to zero. Originality/value: The results of this study support other studies suggesting that factors other than class size are more important in influencing academic performance.