Qualitative Comparative Analysis (QCA) is a case-based method, developed by Ragin (1987, 2000), to analyse medium- and large-n datasets. It uses Boolean algebra to show which configurations of factors in a model are either necessary and/or sufficient for a specified outcome. In the social world, we rarely see perfect necessity and sufficiency but we can use QCA to assess the degree of necessity or sufficiency to find configurations which are quasi-necessary or quasi-sufficient. In this paper, I use crisp-set QCA on data from the 1970 Birth Cohort Study (BCS70) to investigate which configurations of sex, maternal interest, social class and, later, ability are quasi-sufficient for various levels of attainment in maths.