I quite like that idea. I had the same teachers for maths, history and economics in both of my final years of high school (which are the two "assessment years" for lack of a better term) and I definately felt more comfortable in these classes. Probably helped that the teachers were awesome though.
I wouldn't have thought that primary school would be as important though (so years 1 to 7 in Australia) as its more about learning to basics and developing social/learning skills. The actual "learning" occurs in high school.
From first glance, it almost seems like the way that teaching works now, as in the "one year" thing, is more of a product of the old way of teaching rather than the focus on skills and outcomes which exists now. On that basis, too, I like it.
I'd say it has merit, for sure, on face value. I'm not sure how the US system works re: specialised teachers and stuff, so are you saying you would have A science teacher, A maths teacher, A english teacher etc?