The question is whether they got it on the field, locker room, or at a house party. Or whether the cases are even related. If the team had 100 kids for summer try outs, 7 isn’t all that unlikely.
We know teenagers can get it and spread it, especially indoors.
We also know that it spreads poorly outside, and that we have not seen any clusters at the thousands of elementary schools that re-opened in Europe and Asia.
May be that we need to draw the line at middle school age. But, if we are going to take away all in person opportunites for elementary kids to play, I‘d like a better explanation than “6 feet”.