First of all, how do you know he go if from school? He works with you - could have gotten it there. Or really anywhere else he could have gone. To assume he got it at school is a stretch.
But OK, say you are right. I would rather that kids was in a routine, going to school, then having the school quarantine him and all of his cohorts (which should be you too, BTW), then what is going on now. If he was in school there would at least be an attempt to maintain 6' distancing, hand washing etc. Sure it's inconvenient, but after 14 days everyone is back in school. Also, we would know who his cohorts are.
Right now, there is no such effort. let's say that kid plays club soccer. The school is closed, he's got time, but he can't play in CA, so the team heads to AZ to play - often times the same team they would have played in CA. That is happening and that is TEXTBOOK how COVID is spreading. The only youth I know that has gotten COVID got it that way, during a trip to play club lacrosse in UT.
I hear you though, he shouldn't be travelling to play sports, that's his fault. Well, OK, but right now everyone BUT him who is following the rules is essentially quarantining indefinitely with no end in sight. NO WONDER he is breaking the rules!
Which is just a long way of saying, you can either give people a semblance of normalcy and establish some safety protocols for them to follow, or you can lock everyone away and they will find some semblance of normalcy on their own - no rules. Your choice, or I guess in our case in CA, we don't get a choice. Look at the numbers; it's not working.