The purpose of this study is to compare the college enrollment and STEM college major choice rates of graduates of a STEM-focused charter school system to those of students who graduated from traditional public schools in the state of Texas and the USA for low-income, first-generation, and underrepresented groups. In addition, the factors students perceived as important in their STEM career selection were examined. Participants were Harmony Public Schools (HPS) alumni who graduated between year 2002 and 2016. Data were collected through annual and additional surveys via e-mails and Facebook. Data were analyzed descriptively to answer the research questions. It was found that HPS had significantly higher college enrollment rates in all minority groups including female, African American, Hispanic, and low-SES when compared to public school students in the state of Texas and the USA. The second research question revealed that HPS graduates' STEM major choice rates were significantly higher than their counterparts in the state of Texas and the USA in all subgroups including female and students of color. Students' self-interest, teachers, and parents were found to be the top three factors that students thought affected their major choice.