If it had no parking, then the parents would be parked somewhere else and loading and unloading their kids there, and then that would need to be a no-parking zone too.

I guess you could keep doing that until kids just walk to and from school?

Our local school has them unload a block away unless they are handicapped. A kid isn't going to die walking a block. But its pointless because they still allow residential on street parking around the school, and my son has to use a crosswalk where cars routinely park so close to, I had to tell him that the traffic (pretty heavy) on the road wouldn't see him easily, and he should always ease his way into a crosswalk and not assume he would be easily seen.