I am not familiar with that Geometry book but at least some of MacDougal Littel's math textbooks are geared toward gifted students.

I don't know that it is so much a question of getting rid of Differential Equations and Linear Algebra as downplaying/not advertising it. For example, the Pre-Algebra program that DS was in last year was not advertised at all and the Algebra that he is taking this year is not even a program as there are only two students (counting DS) in the district of over 100,000.