The strike, led by the National Union of Teachers, will cause disruptions to some 10,000 schools during the one-day walkout. Teachers threatened a fresh wave of strikes as it emerged that yesterday’s walk-out forced the closure of fewer than one in eight schools.

Unions are considering further strikes over the summer term – which includes public exam season – in a long-running row with the Government over pay, pensions and workload. Government figures showed yesterday’s strike closed just 12 per cent of schools – significantly fewer than previous walk-outs.

Despite the Welsh government having power over education policy in Wales, pay is controlled by the UK government. The UK government has criticised the strike, saying it will cause disruption for children and parents.

The UK Education Secretary Michael Gove has said parents will not understand why the union opposed paying the best teachers more, under plans for performance-related pay. However, that has been disputed by NUT Cymru secretary David Evans.