Yeah, I think that my school could have compressed third and fourth grade without hesitation. Same for fifth and sixth. I started ignoring the system once I got to high school, though. At least for math. The curriculum was abominably slow, so I made my own path.
Old system (2 years ago): Integrated I => Integrated II => Integrated III => Pre-Calc => Calc (very rare.)
New system (implemented last year): Algebra I => Geometry => Algebra II => Pre-Calc => Calc (very rare)
ME
9th: Integrated I (They didn't have room in the advanced class that skipped 8th grade math to let some kids do this in 8th grade.)
9.5: A couple friends of mine had a wacky idea to 'get ahead' in math by taking Integrated III over the summer. My current Calc teacher (the delegate one) offered to do it, even though the school district refused to pay her. (She's one of those people that love math as much, if not more, than I do. Vector-esque, perhaps.) They were among the 8th graders who had taken Integrated I, so they had already finished Integrated II by the time 9th grade was over. I had not. But I was pissed off at being stuck in lower level math. I joined in and worked my ass off to not only complete the class, but also learn everything that everyone else learned over the course of the past year. All of this in 6 weeks. My compadres were proud of squeezing 9 months of class into 1.5. I fit in 18.
10: The school district changed to the new curriculum this year, so instead of Integrated II I took Geometry. I also took Pre-Calculus. This confused the living hell out of the administration. My principal is an ass, so he wouldn't let me test out of Geometry even though I clearly knew (I demonstrated.) everything the course taught. Technically, he did allow me to test out, but I would only get an elective credit, and you specifically need a Geometry credit to graduate. Nobody knows why he is still the principal. I seriously doubt he will retain his position after this year, with the way he's been running the school. "No, we have to stick to the old standards until we are forced to change! We live in an ass-backwards rural town! It has to be this way!" doesn't fly too well with parents.
11: This year I'm taking Calculus at the high school, plus Statistics at the local community college. My principal was (again) pants-on-head retarded and wouldn't let my super-fantastic teacher teach Calculus as a semester class instead of a year-long class, even though it's only a quarterlength class at most colleges. (He didn't think we could handle it.) As a result, I've spent the past few months learning the shit out of math on my own time, because we have literally nothing to do in Calculus any more. We finished everything before the semester finished. We went through each section again out of boredom. Now we're doing random lessons from higher math because my teacher can't stand to do nothing. It's awesome.
12: Next year I'll be in an interesting position. I'll have run out of math. Well, for credit anyway. My Calc teacher finally convinced my idiotic principal to let her teach Calculus II and III as semester classes, with the class being made up entirely of those who took the Integrated III class to 'get ahead' back up there in 9.5. The sad part is that there are no higher math classes at the community college and [INSERT STATE COLLEGE]'s articulation agreement with my Calc teacher means that anything beyond Calc III won't count for credit. (The others do.) In my free time I'll still be unofficially learning more math, though.
End result: Normal students get four years if very basic math and zero college credit. Students who are willing to go nigh insane to learn more math get 8 math courses and end up with 30 college credits. I figure that it shouldn't be too hard to go in between and make at least getting through Calculus standard for high school.