Are they still doing a review of Algebra 1 concepts? If his school's sequence is Algebra 1, geometry, Algebra 2, typically there is some fairly extensive review at the beginning of the year because kids tend to forget algebra while doing geometry. If he remembers everything from Algebra 1, this is going to seem easy, but eventually they will move on to other things that may still seem easy, but at least are new.

Some other things to consider are:

Is there an honors Algebra 2 class available? Might that be a better placement?

Is there an honors precalculus class available? I would not accelerate him into a regular precalculus class if an honors class is available. My son's honors precalculus class was substantially different from the regular class--different text, different peers, and far more covered than either the regular class or the equivalent course(s) at the local community college.

You don't say what grade he is in, but if he's a freshman, what would be the plan for math in his senior year? My son took honors precalculus in 9th, BC calc in 10th, statistics (AP) in 11th, and post AP statistics in 12th. The last two years he coasted, but he also found that he loved statistics (and he is majoring in it now in college).

Yes, they are still doing review, or at least it has felt that way to DS. Because of that, he wasn't too bothered by the repetition, which is why it surprised us that the teacher proposed the move. He had to be enrolled in the new class by today to receive College in the Classroom credit, which is why there was some urgency I guess.

No, honors is not an option. We are a truly tiny school. As far as I can tell there are one or two sections each of Alg 1, Geometry, Alg 2, Financial Algebra. One section each of Precalc, AP Calc AB, AP Calc BC. That's it. So, for his senior year, DS thinks it sounds like either a good opportunity to finally try AOPS Discrete math, or he can dual enroll in Linear Alg, Diff Eq, maybe multivariate calc at community college. But...and this is my dilemma that prompted this thread...maybe he needs to be getting actual university-level coursework at that level, if he's going to be on a STEM track.

Basically, I am coming into this with a strong bias because of my own checkered past with math. After getting 5s on my AP Calc, I placed into Calc III at college. I thought I was being conservative by doing accelerated Calc I/II as a review first, getting a solid foundation, etc. But instead, my previous experience of Calc as a pattern-matching test-prepping multiple-choice subject was really difficult to shake. I sailed through Calc III and beyond with easy As but I hit higher-level math and ran up pretty hard against proof writing and problem solving, barely hobbling to the finish line of my math minor. Since then I have read Lockhart's Lament and The Calculus Trap, I have seen the syllabus and different pedagogy used in Calc as taught at places like MIT, and I have piled a lot of my personal woes on having done Calc in HS. It's the last thing I wanted for my kid. But it's also amazing to see him A) recognized for his strengths, and B) fired up about the opportunity to really work hard in a class. We've talked SO extensively about the difference between school math and mathematics, he did take that year of AOPS Geometry and has seen that math isn't just about knowing right answers, and I'm really hopeful he can avoid some of the pitfalls. But he also got a 276 on his Accuplacer which I believe puts him into Precalc at any CC or university that uses it as an entrance exam. In the lower grades we often say that subject acceleration makes more sense than making gifted kids sit through material they already know in order to avoid small "gaps" of material they don't yet know. It's scarier at this level, the repercussion of gaps feels bigger, but I honestly think the same philosophy might nonetheless apply in this situation. He can cover those gaps over time. I think. I hope.