The QEH school, on Jacob's Well's road, hadn't come to anyone's attention, but while in the area at 1600 it becomes obvious that the primary form of getting the child home is by car, which leaves a problem: where does the car park? Mostly on Jacob's Well's road. The double yellow lines ensure that commuter traffic is kept out of the area, so providing a place for parents to wait.
The lines may say "no parking", but as the parents are sitting inside, they are merely waiting for their offspring, which is not technically parking, more a lifestyle choice for parents.
Up on the side road to Clifton, well, cars such as AG06AWA and A3NUU are doing their best not to block through traffic, by getting up on the pavement and in front of resident's garages. It is this "flexible, shared space" use of city features that enables Bristol to function.
Some cars, like the Landrover WP08YAF also make use of the "school keep clear" section. Note, however, unlike outside Clifton College or Christchurch School, nobody is parking on the pavement here. That is being left as a safe place for children to walk.