A quantitative case study design was employed to investigate the relationships between students' computer and Advanced Placement (AP) course taking, SAT test scores, and their STEM major selection. Study data were collected through an online survey from a multi-school charter school system in which variety of computer courses are offered to 9-12 grade students. The study showed that students' SAT reading, composite (math + reading), and total scores had statistically significant relationship with students STEM major choice. Even though there was not a statistically significant relationship between students' SAT math scores, there was a pattern showing that students with higher SAT math scores were more inclined to choose a STEM major. We also found that there was a statistically significant relationship between the number of students' AP science and AP courses and their STEM major selections. The last analysis revealed that there was no statistically significant difference between those but we found that those who chose STEM majors took more computer courses than those who did not choose to do so.