Purdue is a good match. I would have your son apply EA as applying RD is more competitive as many of their slots for engineering will have already been offered. Since your son attended STEP he probably is aware they accept students into their FYE program and apply to their major second semester. Highly competitive majors require higher GPA’s to be assured a spot. You can be accepted into an impacted major with a lower GPA but it can be stressful. Purdue is a great school. Good luck.