National Education Union
The result of the vote organised by the National Education Union will be "very close" due to delays caused by Royal Mail strikes and bad weather.
Unison is at odds with the National Education Union in a dispute over school support staff.
The call comes after Gavin Williamson was forced to make yet another u-turn on Friday, with all primary schools in London to remain closed after Christmas.
Announced on the eve of the Christmas break, schools have been left hanging as they wait for the details on the education secretary's plan.
Exclusive: Mayor of London warns ministers' words leave teachers exposed to greater verbal and physical abuse at hands of pupils and parents.
Parents, teachers, unions and politicians all have strong views about whether schools should shut. Read these arguments before you decide.
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Stress has seen children vomit and flee exam halls in tears.
Pupils across the country are picking up their results this morning.