They've tried having a traffic warden attend - sadly not issuing tickets - as a warning. This worked. For about three days.
My personal solution, if I'm not alllowed to impose the death penalty, would be to make the children carried in the cars stand up at assembly and speak for five minutes on 'why my parents / guardians think the parking laws do not apply to them'.
A few months ago, there was a fuss in the Evening Standard about someone stickering 4WD cars with 'this car is killing the environment' stickers that were impossible to remove without damaging the paint. Apparently, you could get them by asking a hotmail address. Unfortunately, they didn't say which...
... 'cos I'd love to have some that say 'I don't give a shit about other people's children'.