If the feeder middle school where the kids go to have a middle school soccer team, then those kids are required to play at their middle school (or play club soccer).
If the middle school they attend does not have a middle school team, then they are allowed to tryout for JV soccer at their high school.
Only 9th and 10th graders at the high school are eligible to play JV (and 7th-8th - see above).