Schoolboys in the Philippines are said to be underperforming in human capital accumulation, particularly education, compared to their female counterparts, especially in rural regions. Although existing literature has analyzed the sources of this bias, further research is required to understand its background. Thus, by combining our unique primary data from our own field survey using tailored questionnaires conducted in Marinduque Province and administrative data on the National Achievement Tests (NATs), we compare sources of the persistence of a negative male effect on test scores. We avail of the variations of blindness in rating systems between the NATs and teacher-rating report cards (RCs). Results of sensitivity analysis in regressions support the hypothesis that male students are systematically more likely to receive lower scores when they are evaluated in a non-blind rating system in which teachers know who the examinees are. The paper empirically presents an insightful perspective about Filipino s choolboys’underperformance being further augmmented through gender stereotypes perceived by the evaluators, in this case, the school teachers.