The purpose of this study is to investigate how students' school-level STEM-related factors, motivational factors, and parent/teacher expectations affect their plans for college STEM-majoring. This paper reports on two-year longitudinal study of high school students from a large, public school charter system. Logistic regression results revealed that male (both years) and Asian students (both years) are more likely to consider STEM majors in college (compared to Hispanic students). Other significant factors found positively associated with students' intentions for college STEM major included STEM summer camps, GPA, teacher encouragement, science-efficacy (year-1); and self-expectation and math-efficacy (year-2). In addition, self-expectation was the only significantly different factor accounting for the difference between positive (non-STEM to STEM) and negative (STEM to non-STEM) changers.