This paper employs a unique set of micro-data covering almost one-third of the Dutch labor force, to estimate the heterogeneity of agglomeration externalities across education levels. This paper shows that there is substantial heterogeneity in the relationship between agglomeration and productivity of workers (proxied by their hourly wage) with different educational background. Apart from estimating the impact of the aggregate density of regional labor markets, we also estimate whether the composition of the local labor market in terms of education is related to the productivity of different types of workers. Using the presence of universities as an instrument, we estimate the effect of the supply of university graduates on wages, i.e. the social return to education. We find that agglomeration externalities are substantially higher for high- and medium skilled than for low-skilled employees. We find no positive effects from the presence of high-skilled on the productivity of low-skilled.