Same 3 mothers parking their cars on yellow no parking lines outside primary school

The same 3 mothers are parking on the yellow no parking zig zag lines outside Pyrcroft Grange Primary school opposite a driveway. Arrive before 0850 and stay beyond 0900hrs then pick up at 1500hrs smoking and drinking red bull in dressing gowns in a white 20 plate VW Passat, Red Vauxhall people carrier and another black car. They have been there consistently every school day for 5 weeks until today when parking enforcement were present the mothers were no where to be seen so may have been tipped off.