The National Union of Teachers is urging its members in the Isle of Man to report for work as normal on Monday, even though it's been added to the school holiday.
The Christmas break has been extended by one day, with the new term now due to begin on Tuesday, January 5.
Education bosses hoped to 'bank' the teachers' extra leave, to use as cover for absent staff later in the school year, but that will only work if teachers decide to take the time off.
Branch Secretary of the Isle of Man NUT Karl Flint says the scheme is not the right way to address the problem of staff cover.
He hopes those teachers who can, will report for work:
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