My school allowed changing tiers, and I am very grateful that it did. I had a bad year in my early teens with some mental health stuff, and spent my first year in high school with kids who needed much more time and practice to get a handle on concepts than I did. If I had been forced to stay in those tracks, my life would have taken a drastically different course, as I didn't really need to work to learn. Getting bumped into a higher tier challenged me, and that challenge is what prepared me for college.

Had I gone into college without that work ethic, I almost certainly would have failed out early.