In this study, carried out in different provinces of Spain, we assess the impact of a co-educational science program conducted with children aged 3-6, whose objective is to deconstruct gender stereotypes in science by studying the biographies of female scientists. The evaluative methodology we use is based on analysing the opinions the pupils expressed at a school assembly, and we have applied content analysis to explore how much the pupils learnt about the female scientists, through 401 drawings. The main findings are: (1) 5-year-old children have sexist stereotypes related to the distribution of power between women and men; (2) the program is effective, because the pupils increase their knowledge and enrich their notions of female scientists and their contributions to science; and (3) the pupils do not illustrate situations of indirect inequality among scientists in their drawings, because they only perceive the injustice existing in situations of direct inequality.