No I don't think it would be too difficult to make CTC or RTR work for high school. We are getting ready to do just that with RTR. My boys are not doing the science, they are going ahead with their Apologia curriculum that we have been doing. Same with Maths, we are just continuing our MUS Geometry and Algebra 2.
The rest of it though, we're probably gonna do pretty much the way it is written. We'll be using the extensions for my almost 14yr old and for the almost 16 I plan on pulling a few books from the Ambleside Online curriculum just to beef it up a bit. That curriculum is listed by year and by timeline (sort of) so it's easy to match up where you might be able to grab a couple of books to add to the history and lit. I don't think alot has to be added though to RTR, the books used are comparable to TOG and Ambleside, very rich living books. I love how Carrie has done all of the work for me.
I know there are a couple of threads where Carrie offers some ideas for stretching CTC for high school, I'm not very savvy so I can't link here.
![Embarassed :oops:](./images/smilies/icon_redface.gif)
Hopefully, some one else will pop on and put a couple of links for you. You can always search CTC High school and see what comes up.
Sorry not terribly helpful but welcome to the boards, you'll love it here.