School 'keep clear' markings
The yellow zig zag markings often found near schools are there for safety reasons. They are designed to warn motorists that stopping would cause a danger to children and pedestrians.
The restriction times are as shown on nearby yellow time plates and while they are in force, motorists must not stop for any reason, including setting down or picking up passengers or loading / unloading goods.
Detailed information about road markings and signs is available in The Highway Code.