It does sound like a lot of repetition, but that is built in to a lot of the hs curriculum, at least around here. It’s how they are able to offer advanced and AP level work to anyone who wants to take it. But repetition certainly varies by class- here kids take calc BC right after what they call “pre-calc”- there is no point in taking AB because the material is all covered in the pre-calc and AP BC course, unless kids need a slower pace/less material and that repetition.
It seems if one is not comfortable following the typical school progression, one really needs to look at specific details of each class and subject (and that’s probably why deviating from the standard path is strongly discouraged here- they make it really difficult to switch stuff around and are inflexible with someone not fitting into their pathway- because it creates extra work and responsibilities, and it’s easier to just force kids to do repetitive or lower level work than try to figure out whether they can skip stuff. (This is certainly influenced by a couple kids per year who end up requiring extensive tutoring after skipping ahead anyway- the teachers are very patient but it must be super-frustrating for them to essentially teach the skipped course material one-on-one every day after school...and they probably forget all about the ones who are able to do it successfully). There must be an easier way...
