I should think if this ever does become law, we will see a dramatic rise in 'sick relatives abroad' that need to be visited. Failing that, parents will simply phone in and say their children are ill and won't be in for a few days, but oh of course it's the end of term isn't it? All that is likely to happen is an increase in dishonesty, and aren't we trying to encourage the children to be upstanding honest citizens in society? Will passport control be looking for supporting evidence (eg doctor's certificate) when they see someone under the age of 16 go through during term time? I frequently get equestrian from parents because of restrictions of flight times, ie only one or two flights a week meaning they have to go Thursday to Thursday etc.
Dave