We participate in a CC group as well and I tutor a Foundations class. My kids are not in Challenge yet but I’ve visited the class and looked into the books and curriculum to determine if it’s a good fit for our family and whether I might teach any of the levels in the future. I can give a brief overview. Challenge A-B, which are roughly 7th-8th grade, utilize a classical model for science but do not use a curriculum. Here is what they cover:
Chall A: Fall- Natural Science- each week a topic is introduced in class related to the plant or animal kingdom, at home the students write a 3-5 paragraph report on that topic utilizing 2+ sources
Spring- Anatomy- each week a system or part of the human body is introduced and the students learn to draw and label it, at home they practice that drawing and learning definitions of each item they label, they have a quiz on each body system in class where they draw & label it and write out the definitions
As part of the apologetics strand, they also read “It Couldn’t Just Happen” and memorize these catechism questions: https://quizlet.com/5248215/challenge-a-catechism-questions-flash-cards/
Chall B: ~10 weeks- History of science- each week they discuss a scientist and then write a paper using 2+ sources
~6 weeks- Science Fair- learn the scientific method and work on their own science fair project
Origins (not sure how long this runs)- read Defeating Darwinism, they learn how to outline as they are reading the book and then discuss in class
Chemisty (a couple weeks?)- this is a short unit on chemistry written by a CC employee who I believe has a background in English Lit (!). I pointed out a few errors and hopefully they will be corrected in the next edition
As for Chall 1-4 (high school), these classes use Apologia but the class time is primarily for doing the lab, so you could easily use something else at home. I think physics is the only exception, they use Saxon and it does not have a lab component.
With regard to the memory work in Cycle 3 that relates to origins, they definitely made a huge mistake in their definition of The Theory of Evolution and they are aware of it There is a process for corrections where you submit your correction and sources to back it up, I was planning to do that but the academic team let me know that they had a plethora of feedback and it will be corrected in the next edition. FWIW their “definition” came from “It Couldn’t Just Happen” but it was a definition that included 3 statements and they only included the part to do with abiogenesis, which clearly made their “definition” incorrect.
In general, I find CC to be weak in science which is very typical of a classical curriculum. However, because my husband and I are strong in science and math, we have no problem covering those subjects in more depth at home. My kids will probably do bio in 8th grade with the Miller & Levine text. When their CC class covers bio in 10th grade, I will do AP bio with them at home and the labs in class will be good practice.
I appreciate the strength CC brings to the other subject areas and the ability to do group activities that wouldn’t work at home (Foundations- weekly presentations, Challenge- mock trial, debate etc). I think the teacher is a huge factor in how the class discussions go on topics related to origins. You might see a strong ID emphasis, but it will depend on the teacher.