Green spaces around schools contribute to children's health and wellbeing. However, only a few studies have examined whether green space provision around schools in urban and rural areas are equally available across socioeconomic groups. We assessed whether and to what extent the green space provision of public primary schoolyards differs cross-sectionally across demographic and socioeconomic neighborhood profiles in the Netherlands. A fine-grained measure of green space (e.g., lawns, hedges, and trees) was applied to 5,773 school locations centering buffers at 50 m, 100 m, and 500 m. Fitting spatial lag regression models to the data, our results showed robust and inverse associations between available green school outdoor environments and low-income and less-educated neighborhoods. The percentage of non-Western migrants was positively associated. No evidence showed greenness around schools differing across levels of urbanization; however, schools with subsidy schemes supporting schoolyard greening tended to be greener. Our overall findings highlight socioeconomic disparities in green school outdoor environments across the Netherlands. To bridge this gap in environmental justice, we advocate for each child to have the ability to benefit equally from schoolyard green spaces by enabling more comprehensive greening subsidy schemes.