As an example of why I don't think he should skip Algebra I notwithstanding chapter pretest scores of mid-80's to mid-90's: I have seen him solve an equation in five steps instead of 4.

The idea is that he fills the 'gaps' as he encounters them. Too much repetition => boredom and decrease in motivation. (Much discussed in this forum.)

Example (an actual Alcumus AOPS problem): "Represent 39/2500 as a decimal.". DC does long division, then sees a shorter solution (multiplying both parts by 4) - he'll know in the future to look at the particulars of the numbers first.

(I'm actually not trying to sway you one way or the other, because your final decision may be driven by very practical considerations - e. g., whether he'll have to work completely on his own, without outside help.)