"and avoiding a need to increase the length of the school day"

Yes.. teachers do need a few hours off work to get some sleep at night...

My wife's school day ends when she switches her laptop and mobile phone off
minutes before she goes upstairs to bed...

.. if she can avoid restless nights worrying about the next day's problems at school...

Nigel - Yes, those lazy lefty teachers only want to feed kids in school at taxpayers expense,
so they can have an easier life skiving hard graft...