My son was homeschooled for K-4, skipped 5th, did 6th at a tiny private school where his class was combined with the 7th graders (with additional acceleration in math), skipped 7th (because he had done it the previous year in the combined classes), and did 8th at the private school. While the EF demands ratcheted up in each skip, the intellectual demands stayed fairly constant. So, school was challenging, but not in the right way and by the end of that year, he was begging to be homeschooled again.
So we did high school level work at home for two years and then he decided to go to the public high school as a 9th grader. He has been there for the past two years, and to the school's credit, they placed him properly in math. But the other classes, particularly English and social studies, have been a joke. So midyear this year (10th), we decided to homeschool him in those two subjects again. Next year, he will take three AP classes at the high school and three college level classes at home. And we are thinking about either graduating him at the end of next year with a gap year or doing a very non-traditional senior year.
The skips were an interesting exercise. I'm sure they work for some kids, but in our case it seemed like we just ended up trading one set of problems for another, and the main problem, the lack of intellectual stimulation, was never solved.
