Christmas,
You haven't broken any laws, but you are acting like a bit of an arrse.
You say yourself your dropping your kids off at school. They have to live there. How do you know the reason they want to park outside THEIR house. Could it be the car was recently broken into because it was parked out of site as someone who couldn't be arrsed walking to school decided to park there. Or that they have need to park it outside eg pregnant women in the place.
I don't know your situation, but I have had arguments with Mums who drive a shorter distance than I walk to collect the kids from school, then park in front of someones house. There's no need. Instead of spending £500 a month on Kiddy Gyms and Childrens Yoga, they could leave the chelsea tractors at home and walk it.
If there is space a few car lengths away, why don't YOU park in it.