Since I took ds13 and ds10 out of public school a year and a half ago, they have been doing most of their schoolwork together. I keep it somewhat simpler for ds10 -- not in terms of content, but in the amount of work that he's responsible for. Examples: he can choose 3 of 5 comprehension questions for literature today, his essays don't have as many sentences as his older brother's, and I make his end-of-semester exams a little shorter. I have tried to choose curricula that are not necessarily lighter in content, but perhaps presented in a more interesting way than your average textbook to help keep ds10's interest. Lots of Ellen McHenry science with all of the accompanying activities and games, SOTW coordinated with Human Odyssey and Mapping the World with Art, LLLOTR this year with an accompanying audiobook, Life of Fred etc.
Now I have a rising 9th grader, and I'm torn about what to do next year with all of the rigor that high school requires. Do I let my rising 6th grader tag along, or do I craft his own program? In many ways they are on the same level. They'll both be through Algebra 1, at the same stopping point in social studies, have finished LLLOTR together, taken the same IEW writing and grammar programs... I'm sure it helps a lot that they are playmates and generally prefer to learn together. However, these programs I'm intending to use next year seem like a significant step up. I'm not so worried that he can't grasp/remember the concepts, but more that they'll be presented in such a dry "adult" way that his eyes will glaze over and he'll shut down. I'm also concerned about social studies and literature being age-appropriate (sex, violence, language...) for him.
Have any of you let your younger AL tag along with your high school student? How did it turn out? Any advice?