My oldest daughter did the Apologia YE Botany in 6th grade, mostly on her own. This was long enough ago that there were none of the notebooking journals and things that go along with them now, though she did answer the questions and do a lot of botanical art to go along with her studies, because she enjoyed it. I agree with Jamie that the series would be best used with kids at least 2nd grade, and the botany book was perfect for a 6th grader to use mostly independently. I haven’t seen the newer studies (anatomy and chemistry?), but I did use the Flying Creatures book with my 2nd daughter when she was about 4th grade and I briefly used the Astronomy book with her when she was younger than that.
I was nowhere near as CM then as I am now. With my current almost-8yo I’m doing interest-led living book science and nature study and it’s working wellfor us. We used Outdoor Secrets for 1st grade and that was wonderful.