Homeschooling is years of trial and error.
My oldest had Saxon Algebra2 and Saxon Physics this year. We did the first lesson in Physics and realized it was impossible for him to do. He got a 40% on the first lesson, and we have a video teacher to go with it too. The Algebra2 he's been managing so far (1 week) with.
I discovered the Physics actually needed to come after Advanced Math...which is after Alg2. oops. I just went by all the curriculums that state Physics is the 12th grade Science. It was not a good fit.
So it all got packaged up and sent back to CBD. That was a $100 program. So now what for science?
Well, I have a set of paperback books by an author named Tiner that haven't been read yet by anyone but dh. They are on Physics, mathematics, Earth Science, Medicine, Chemistry, and Biology. They are overviews of each subject with chapter quizzes. So we will make good use out of those for now and it might just fill out this semester. Next semester I'll have to think of something else. Ds has had physical science, biology and then Marine Biology in his high school years.
The one plus I found to buying new books instead of used (which typically I do) is that at least I can return them. If used, I have to try to resell them.