This paper is a direct extension of the paper of Jones (2007). This author presents a simple Mincerian approach to endogenizing schooling time in market economy. His specification is closest to that in Mincer (1958) which does not take into account the social benefits of education. Our note extends his paper on the social returns to accumulation of human capital, with particular emphasis on the social returns to education which are given by the sum of the private and external marginal benefits of a unit of human capital. In other words, we study the problem of human capital externalities which comes from social interactions. We propose a policy of decentralization of the optimal education .