Actually, DS already aced the Pre-algebra course and a national Algebra readiness assessment last year. This year he is enrolled in an online Algebra course arranged by the District office, who also provides a live instructor one day a week.
DS decided to implement a single skip to Pre-algebra last year rather than a double skip to Algebra. He wanted to make sure that he had a super strong foundation. So you may have an excellent point regarding the overlap. It makes sense that he is able to score mid-80's to mid-90's on the Algebra chapter pretests by extending what he learned last year in Pre-algebra.
However, I don't regret having DS take Pre-algebra last year because he is not as strong in Geometry and about 40% of his Pre-algebra course covered geometry and trigonometry topics. Of course, the trignometry topics were cursory and focused on sine, cosine, tangent, secant, cosecant, cotangent and basic real world applications.
