Wow. We had elementary schools (K-4), middle schools (5-6), Junior high (7-8) and high school (9-12).
In our district, it helped us know a lot of the kids. Because the lines for the different schools were drawn differently, it was very easy for two kids to go to the same elem school, different middle and jr highs, then the same high school. It was interesting.
I have NO idea how it would have affected test scores. All I know is that I turned out alright.