There will undoubtedly be more needy cases where the single mum drops off little Johnny at school on her way to her daily 23 hour shift at the pit. However, certainly at my local school, 99.9% of them are just lazy and drive to and fro, often only 3 or 400 metres each way, twice a day. The only one I know who doesn't is a guy I sometimes chat to, he works for network rail, finishes work at 1500hrs and drives like a loon to cover the 7 or 8 miles to school in 15 minutes.
But the bulk are simply fat, bone idle lazy. Else why are the roads so quiet during school holidays?