My singing voice was baritone in high school and now in college while taking voice lessons it went up to tenor??? What did I do?

A few things could be at play here. First of all, the major adolescent voice change isn't the only one you'll experience in life--our voices are biological instruments, so they will change with our biology. My range has been all over the place within the past 20 years. Another huge thing that could cause your fach change is that (presumably) your technique is getting better, so you're able to hit higher pitches and sustain a more tenorial tessitura. The last thing--and I hate to say this--could be a fault with your teacher. It's best to learn to sing. Period. People who teach different voice types dramatically differently or who ask people of one fach (in your case, I'd be willing to bet you're *actually* a baritone) to sing in another one do exist, but the students' stories usually don't end well. It can be quite harmful to train "as a tenor" if you are truly a baritone. Then again, I haven't listened to you to judge your fach, and your teacher has. So assuming your teacher is legit and doing the right thing, it's some combination of physiology and technique that's allowed you to move up; most professionally-sized tenors start out learning in the baritone range. Hope this helps!