I'm not letting on my actual opinion on this, but I am curious to know what others think.
I live opposite a primary school. I knew the school was there when I bought the house. Most days my car is not on my drive because I am at work, but I have on a couple of occasions come home to find a car there.
I haven't approached the parent on these occasions and have just parked elsewhere until they leave
This parent regularly uses the drive (must assume I'm not in) for 10-15 mins each morning and afternoon. There is usually other parking available, but further away
Driveway is a shared drive for 4 cars, I own one of the spaces and there is a Private Parking sign up across all four spaces which was there before I moved in.
YABU - it's fine because you're not using it most of the time
YANBU - they're CFs