I have the final say in all educational, legal, medical and religious matters.
It is impossible to enforce an order wherein one parent has a majority of the time/primary custody and the OTHER parent has "final say". It is also, quite often, considered contrary to public policy to award joint legal custody while giving one parent final say.
AND, if you really had "final say", why on earth would the judge order you and Mom to work out where the child would go to school? If you have "final say", you can just say "Child will attend X school." And that would be the end of that.
Honestly, I don't think you understand what happened in court. And if this is REALLY what the judge ordered, it is impossible to enforce/abide by. I am speaking as someone whose ex had "final say" in all matters, as you believe you do, but *I* had primary physical custody (60% time). It was modified by the judge at the first opportunity, because it was unworkable. In fact, the judge said "Who signed off on this?!" (it was him).
I also sincerely doubt Mom is going to give up primary custody voluntarily. Why would she risk that, so that you could avoid driving the child to school when you just took her to court in an attempt to get exactly that ordered?
If Mom enrolled the child in a K12 online school, he would be enrolled in a "public school", AND be homeschooled.
Finally, the judge ordered that Mom retain primary custody. I don't anticipate said judge being entirely pleased if you present an order for signature that makes YOU primary custodian. The judge, after all, seems to think the opposite is in the child's best interests. If you want the child enrolled in your district, which is what you apparently wanted, then you're going to have to figure out transportation.