We get asked this a lot. Some programs will do Algebra I, Algebra II and then Geometry. While that is a good model, we have found students are more prepared for a course like Algebra II which has more abstract Algebra than Algebra I by taking Geometry first.
We also find that students sharpen their Algebra I skills during Geometry as the kind of Algebra used in Geometry comes from Algebra I which really supports students in preparing for Algebra II.
Mr. D also believes that Algebra I trains left brain thinking while Geometry trains right brain thinking which creates a whole brain thinking approach to Algebra II.