Recent discussions on the spatial distribution of educational resources center on exploring the social-spatial equity of the allocation of educational resources in the city. Following the research about spatial accessibility of urban educational resources, and based on the data about public primary school districts and residential districts in Nanjing, China, we propose a social-spatial accessibility computing framework to measure different degrees of accessibility to different public primary schools across geographic, opportunity, and economic dimensions. Results show that: (1) the geographic accessibility to schools in the inner-city is superior to those in the outer-city, but the spatial differences are rapidly shrinking as schools are being incorporated in the inner-city and built in the outer-city;(2) the opportunity accessibility to schools in the inner-city is inferior to those in the outer-city, and the access to the educational resources in the inner-city, especially high-quality education resources, becomes more scarce, due to the demolition in the inner-city and the construction in the outer-city;(3) economic accessibility is associated with the grade of the school, which, in the top school district, is the minimum, while there is a large decline in economic accessibility, with the overall soaring housing price in Nanjing. In other words, family background differences appear to have a significant influence on accessibility to high-quality educational resources (HQER). As a result, misallocation of educational resources, especially HQER, restrict social mobility and further exacerbate urban socio-spatial differentiation.