Hey, I was homeschooled, and my ma threw Saxon books at my head, and I taught myself advanced algebra and calculus as a highschooler. I was a darn good student if I do say so myself, and not turned off to it in the least. Heckuvalot more interesting than history or lit...
The above is anecdotal and I was the exception rather than the rule because I was a frickin' geek, but I disagree with your assessment in general. High school math is not supposed to be FUN. It is supposed to be functional, and if that means grueling and repetitive to get the message across, then so be it. Good students will hack through it and do what they must to get to more interesting stuff.