BACKGROUND AND AIMS: Cannabis use is increasing among women of reproductive age, warranting a greater understanding of the impact of prenatal cannabis use on offspring developmental outcomes. We tested for a potential relationship between prenatal cannabis use disorders (CUD) and offspring educational outcomes across primary and secondary school. DESIGN: Data were drawn from the New South Wales (NSW) Perinatal Data Collection, which included all live births in the Australian state of NSW between January 2003 and December 2005. These were linked with the NSW Admitted Patient Data collection for mothers and offspring, and the NSW National Assessment Program - Literacy and Numeracy (NAPLAN). SETTING: New South Wales, Australia. PARTICIPANTS: A total of 189,558 offspring who completed the NAPLAN in grades 3, 5 and 7 (resulting in 568,674 examination periods). MEASUREMENTS: The exposure variable was ICD-10 Cannabis Use Disorders (CUD: F13.0-F13.9). The study included five outcome variables measured at three time points, as not meeting the minimum national standards for: (i) numeracy, (ii) reading, (iii) spelling, (iv) writing, and (v) grammar and punctuation. FINDINGS: In unadjusted analyses, prenatal CUD was associated with an increased risk for not meeting the national minimum standard of all outcomes [odds ratios (OR) ranging from 3.42 (95% confidence interval (CI)=2.94, 3.99) to 4.17 (95% CI=3.55, 4.91)], with no evidence for an interaction across time. However, the associations attenuated greatly after exact matching by covariates, with reading and numeracy no longer associated with prenatal CUD, while the increased risk of the other outcomes ranged OR=1.31 (95% CI=1.09, 1.57) to OR=1.40 (95% CI=1.17, 1.68). CONCLUSION: Socioeconomic status appears to confound the association between prenatal cannabis use disorder and poor educational performance in offspring.