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).
