Of the estimated 0.6 million teachers employed at government schools in Pakistan, 43 percent have not received any professional development training. A considerable amount of research has focused on the effects of teachers' psychological characteristics and academic qualifications on subsequent student achievement but there is limited evidence on the related effectiveness of school-based professional development training received by teachers on the educational outcomes of students. By using school-level data between 2013 and 2018 from over 21,000 schools in Pakistan from the Annual Status of Education Report (ASER), this paper assays the relationship between the number of schoolteachers who had received professional development training and student enrollment in schools. A fixed effects estimation yields two important results. First, the total number of schoolteachers who received lengthier school-based professional development training had a stronger and larger positive correlation with student enrollment at a school. Second, the total number of schoolteachers who received school-based professional development training had a stronger and larger positive correlation with total enrollment at girls' schools, compared to boys' schools. Future research should focus on the mechanism behind the heterogeneous effects across gender as the literature quantifying the magnitude of such mechanisms is an emerging area of interest.