This study examined whether there were gendered patterns in STEM endorsement choice in the Houston Independent School District (HISD) and how those patterns changed over time, in the wake of a policy change to guidance counseling. The first students required to choose high school endorsements were freshmen in 2014-2015 and graduated high school in spring 2018. The second cohort of students required to do so were freshmen in 2015-2016 and graduated in spring 2019. Students in this second cohort met with their guidance counselor during their senior year to check in on their endorsement progress; this meeting was called the Personal Graduation Plan (PGP) check-in. This was a new district policy implemented beginning in fall 2018, which means that the first cohort did not experience the PGP check-in, while the second cohort did. This study reveals gender gaps in STEM endorsement choice among ninth-grade students. For the high school graduating class of 2018, which did not experience the PGP check-in, female students were less likely than male students to choose the STEM endorsement at any point during high school. However, for the high school graduating class of 2019, which did experience the PGP check-in, female students were less likely than male students to choose the STEM endorsement upon high school entry. Importantly, however, this gender gap in STEM endorsement choice nearly disappeared by high school graduation, suggesting that individualized counseling efforts might be a strategy to improve female retention in STEM.