We did Apologia Science + Nature Study with our 6th grader last year. It works out great to do one about 2-3 times a week, then enjoy nature on Fridays.
Just my personal opinion… I believe the Young Explorer series is recommended for K-6, but I would not use them before 2nd grade. They are pretty in depth and even I struggle with all that information sometimes. The key is short lessons just 2 – 3 tines a week with narrations.
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.
You can find lists of living science books we recommend by downloading the free samples of our living science courses.
In addition to the book lists in our science courses, I recommend most books by
Jim Arnosky
Millicent Selsam
Nic Bishop
Sandra Markle
Robert McClung
Gordon Morrison
There are many other authors of living science books, but the above list is a great starting point. Each of the listed authors has written several books on nature/science topics, has a passion for nature/science, and has a “living” writing style.