I resisted the urge to jump right into this thread when it started. I'm glad I did, because others have pretty much said what I would have said about the legalities and semantics of being or not being a "student".
I'm posting now to ask the OP to consider the premise behind their original question. That being, the desire to remain a participant on your high school team after you have graduated. I would encourage you to read through the
thread about transitioning from being a student to being a mentor. The general advice from those with experience is that you need to separate yourself from your former team, take at least a few years away from FIRST, and consider returning as mentor when you have your degree.
I understand your desire to continue to participate on your team. The fact that you want to is a credit to FIRST, in that the program has made STEM enjoyable for you. You are exactly what FIRST aims to produce, high school graduates who intend to pursue careers in STEM fields. But, remaining on your high school team as a "student" after you have graduated, especially in a leadership position on the team, isn't fair to the other students on the team. They have put in their time, growing into those positions. It's time to allow them to move up.
I'm going to try to phrase this in as kind a way as I can. The fact that this isn't immediately obvious to you is a sign that you aren't ready to transition to being a mentor, either. Being a student on a FIRST team is about being all you are capable of. Being a mentor is about using your industry experience and life experience to help the kids be all they can be. So, follow the good advise given on the thread I referenced and take a few years to get your degree and gain some industry and life experience. Then return to FIRST and be a fantastic mentor. But, for now, it's time to let go and move on to the next phase of your life.