As for the whole middle school/junior high thing. We have a few different kinds around here, depending on the district and the school itself.
At my old elementary, it used to be K-6, but was switching my year to K-5, and my class was the first group of 6th graders to go to MS. But now that same elementary is K-8 but is only one of 2 to be so, the rest are K-5. But, I moved districts in the 4th grade and it was still the same K-6. In a neighboring district, they had school for K-4, 5-6, 7-8, 9-12. Weird. All districts I mentioned had 9-12: fresh, soph, jr, sr.