It's hard to know for sure, as our school is quite opaque and close-mouthed when it comes to questioning the math curriculum; also, they don't really follow any one textbook but use a lot of district-designed materials, so it's hard for me to know where units would traditionally fit, etc. For example, DS's 7th grade math has already covered several algebra units, they also do a bit of geometry, graphing, etc. DDs geometry class just spent a while on some trigonometry, etc- as you noted, the common core units are aligned differently.
I *think* our school is offering compacted 8th and 9th (algebra), though they don't call it that. All kids are together through 7th, then there is a split, where more than half the kids take common core algebra in 8th, the remainder take common core math 8 and then algebra in 9th. My DD took common core algebra last year, and I assume it was a compaction of math 8 and algebra, though as noted I am not certain. Overall, I think it was ok. It was unbearably slow moving for her, though, despite over-the-top warnings from all the counselors and math teachers about how fast-paced it would be. Just lots of repetition and review for her, but DD is an outlier in this class. I think it was a stretch for some kids, (hence the repetition and review) but the exam scores were generally considered good. There were a couple of minor topics that the class did not cover before the common core exam (but because there was nearly a month between their common core exam and their regents exam, they covered the material then; I don't recall what topics they were, and as I said they were considered minor).
This is the only real "tracking" point our math program has- kids can then take honors or regents level (or remedial) classes, based on teacher recommendations (which are easily and frequently over-ridden by a parent request, so essentially all kids can take honors math if they choose). As an aside, this is quite evident in honors geometry, where about half my DDs class is sophomores (meaning they didn't take algebra in 8th grade, the path the stronger math students would take). Ugh. According to DD, they struggle. Lots of use of the tutoring provided in the school's learning center and reportedly of outside tutors as well. Thankfully, the aforementioned repetition and review are much less in this class, and the pace is better (though still slow for DD).
