Childcare costs are often viewed as one of the biggest barriers to work, particularly among lone parents on low incomes. Children in England are typically eligible to start school - and thus access a number of hours of free, full-time education - on 1 September after they turn four. This means that children born one day apart may start school up to one year apart. We exploit this discontinuity to investigate the impact of youngest child starting school on welfare receipt and employment patterns amongst low income lone parents. In contrast to previous studies, we are able to estimate the precise timing (relative to the date when full-time education begins) of any impact on labour supply, by using rich administrative data. We find a small but significant effect of school entry on both employment and welfare receipt (of around 2 percentage points, or 10 per cent), which peaks around 10 months after the child starts school. This suggests that the expansion of public education programmes to younger disadvantaged children may not by itself encourage many low income lone parents to return to work.