I've heard EXCELLENT things about the Bob Jones curriculum and how well students do in secondary education using it. I was customer service manager for a tiny art textbook publishing company for a while, and we'd have parents calling often for supplementary materials for home use, so I got to speak with a lot of them, and also teachers who received students who had been homeschooled using it. Many ended up skipping grades, never mind achieving top marks.
Does your state allow homeschooled students to take advantage of other programs offered at public schools, like after-school programs such as drama or debate, or a book club? Maybe taking part in something like that may alleviate some of the "public school itch" if they are that interested in it.