Our elementary schools are k-6th, our middle schools are grade 7 and 8th and 9-12th in High School. I think before my own time in school (I'm 32 now) they did have 6th grade in with the 7th and 8th grades but not when I was in school and not now.
A nearby school district moved their 5th grade to middle schools this year. They are now called Intermediate Centers grades 5-8. They did it totally because of budget problems. Their elementary schools were over-crowded, so they moved the 5th grade up. I wouldn't like it! I know that the staff works hard to keep the 5th graders away from the 8th graders though. In our school district, they talked about creating K-2 schools, 3-6 schools, 7-9th grade schools and 10-12 for high school. It never made it past debate, which, everyone was against. We're standard K-5, 6-8 and highschool.
our district holds two k-3 schools, one 4-5 school, one middle school (6-8), and one high school (9-12) the only thing different is that all the schools are together in one complex and the buses are wierd the two k-3 ride together and the schools are split alphabeticly (A-K in one and L-z in the other) the next bus runs for the 4-5 school and 6-8 middle school together, then the high school runs alone.
In our town, we have k-4, 5-6, 7-8 and 9-12. WE are one of 3 districts in PA that splits them like this. Our k-4 level is made of up 5 elementary schools, at the 5-6 level, they are all in one building.
6 graders don't participate in sports and certain after school activities due to the fact that a lot of schools around us only have 7th and 8th grade in their middle school.