Our middle school has both a 7th and 8th grade team, but when they were short 8th graders, they asked 7th graders to fill in. But our junior high teams are not actually sanctioned by our school. We only have one middle school so obviously the players all attend the same school, but all fees and funding are done through our city's Parks and Rec. Dept. (For those interested in starting a junior high team, your city's Parks and Rec Dept may be a place to start.) The junior high doesn't have a field so city fields were used for practices and games.
We didn't have many schools in the area with junior high teams so away games were all parent transport (up to an hour away), the fields were not always well kept, and umpires cancelled frequently. Rightfully so, high school softball came first, so if one of their umps cancelled, they pulled ours from junior high.
Because a lot of the fields we played on were set up by coaches/parents right before the game, my dd broke her ankle sliding into home (she was safe!), when home plate had only been partially secured to the ground (missing 2 screws).
Unfortunately this put her out of commission until July of last season. It was a painful summer attending numerous tournaments watching her sit on the bench with a cast and crutches so this year (8th grade) we won't be playing junior high ball...but will try to attend games to cheer the teams on.