Are they going to continue to offer AP Calculus BC for the top level kids? If so the kids will get to the same place in the end. Most places I know ones takes AB or BC calc, not one then the other. And that is how the AP system sells the class. I was surprised to see the current Calculus sequence. The question is it enough for your kids? Will these TAG classes really be more difficult. My son would be happier if the classes he was taking had more proofs in them and did more abstract math.
Even though it doesn't say anywhere in the document about Common Core, if you are in the US I suspect that is what is driving this. Is this a public school?
I hope that AP Cal BC is still on the table. They are still offering it this schoolyear but who knows what happen next year. My DD13, 8th grader, is doing Geometry and she will be in that TAG track. DD10, 6th grader, is doing Algebra I now and she will hit that AP Cal BC in 11th grade anyway and she will have to do dual enrollment or something else.
Yes. It is a public school. The kids hope to get as many college credits in HS so that we don't have to spend much on their college tuition (they would like to have a new car instead)

Well, our common core sequence ends with calc BC. Theoretically, more than half of the graduating class will be on this track, though there are several other options for senior level math courses (a dual enrollment calc class, ap stats, etc). So this is with what I believe is one point of compaction,in 8th grade. Admittedly, we are in a high ses area with an educated population.
And yes,bluemagic, it is not enough for our kids, but as you and others noted, I think the best place for acceleration is certainly earlier rather than later. And for the district as a whole, I think the common core program has been a really good thing, limitations for gifted kids notwithstanding. Many more kids are succeeding at higher level math, and I do think the courses are much deeper.
For what it's worth, we have a relative who excelled in her middle school math program, one of the top public schools in their (admittedly low-performing) state. She was accelerated and sailed through algebra with As. For high school she is attending a top boarding school known for math instruction- within the first few weeks of school there, she was moved down two levels (to the lowest level offered) in math. Apparently she was skilled at solving basic "plug-in" type problems, but their math instruction requires a lot of explanation and reasoning and she was not proficient at this, and needed a fair amount of remediation. So far, from what I have seen the common core classes have been much more successful in encouraging this type of thinking and problem solving.