Receiving an education is essential for children living in poverty to fulfil their potential. Success in the early years of schooling is important as children who repeat grade one are particularly at risk for future dropout. We examined early life factors associated with grade repetition through logistic regression and explored reasons for repeating a grade through parent report. In 2012–2014 we re-enrolled children aged 7–11 years in rural KwaZulu-Natal who had been part of an early life intervention. Of the 894 children included, 43.1% had repeated a grade, of which 62.9% were boys. Higher maternal education (aOR 0.44; 95% CI 0.2–0.9) and being further along in the birth order (aOR 0.46; 95% CI 0.3–0.9) reduced the odds of grade repetition. In addition, maternal HIV status had the strongest effect on grade repetition for girls (aOR 2.17; 95% CI 1.3–3.8), whereas for boys, it was a fridge in the household (aOR 0.59; 95% CI 0.4–1.0). Issues with school readiness was the most common reason for repeating a grade according to parental report (126/385, 32.7%), while school disruptions was an important reason among HIV-exposed boys. Further research is needed to elucidate the pathways through which HIV affects girls’ educational outcomes and potentially impacts on disrupted schooling for boys. Our results also highlight the importance of preparation for schooling in the early years of life; future research could focus on gaining a better understanding of mechanisms by which to improve early school success, including increased quality of reception year and investigating the protective effect of older siblings.