Calc BC is a hard class! My D22 went straight into it from Honors Pre-calc, and the class created a group chat and stressed their way through it together. It was a mix of juniors and seniors in there depending on what track the student started in middle school.
Just know that usually a 60% will net her a 5 on the AP exam – the material is that hard.
D26 was on that accelerated track but didn’t have the best experience in Honors Pre-calc, so her teacher recommended her for Calc AB as a junior instead. That’s rarely done at her school, and we were unsure about it at the time, but it turned out to be a great option for her. She loved the AB teacher (asked him for a rec letter), and this year she’s having a much easier time in Calc BC because of it. (At least until next semester when the AB portion will be over, and it will be all new material, LOL.)