From what I've seen from tutoring 3 younger siblings in math throughout their high school days, I think they should spend the first 3 years of high school drilling Algebra into their heads. Then in the last year they can spend half a year on geometry and half a year on trig.

From what I've seen the biggest problems my sibs had with higher math wasn't the higher math, it was the algebra underlying it. They get one year of Algebra in 8th grade and the move on to Geometry assuming they have mastered it, but they havent.