The first strike to take place in a free school was held today, following a row over controversial plans to introduce what has been described as a “zero-hours” contract for teachers.

National Union of Teachers (NUT) members at the STEM Academy Tech City in Islington, north London, voted for a series of strikes after the school warned of “legal consequences” should staff not agree to new contracts issued before Christmas.

The NUT claimed that a paragraph in the contracts equated to a zero-hours deal, with the school reserving the right to “temporarily lay [teachers] off from work without normal contractual pay or to reduce your normal working hours and reduce your pay proportionately”. The row also centred on the school’s refusal to officially recognise the teaching unions.

An initial wave of strikes were called off last week after the school agreed to talks with the union, but the NUT today claimed that the school had “reneged on their earlier commitments” by failing to hold the talks soon enough.

But principal John O’Shea described the NUT’s “ludicrous” decision to press ahead with strike action so quickly as “unfair and irrational”.

He told TES that staff had been issued with a new contract last week addressing “all of their concerns” regarding holidays and sick pay, with the offending “zero hours” paragraph completely removed. Mr O’Shea said he had also told the union that the school would be willing to officially recognise it.

At a “heated meeting” on Monday, Mr O’Shea said he had been presented by the NUT with a recognition document to sign, but told the union’s representatives that he would need to take legal advice first.

“There’s no way I could sign a legally binding document like that in one day,” he said. “It’s ludicrous. To go on strike today is completely unfair and irrational, and it’s not doing the students any good.”

NUT members at the school are planning to take five days of strike action in the dispute. A notice on the school website said that no lessons would take place today or tomorrow. The union confirmed that members also plan to take three further days of strike action next week, from 11-13 February.

Bob Stapley, the NUT’s regional secretary for London, said: “NUT members are keen for a swift resolution to this dispute so as to minimise any potential disruption to students’ education.

“The NUT has indicated its willingness to meet with management at the earliest opportunity. We are, therefore, disappointed that the school’s management are unable to make themselves available to meet with us before 13 February, which would be the fifth day of strike action.

“NUT members hope that the school management may be able to rearrange their diaries and make this meeting a more urgent priority.”