Thousands of teachers from across Portugal marched through Lisbon on Saturday to protest against a proposed €1 billion (£850 million) cut to the education budget.
Teachers union Fenprof estimated that 30,000 teachers marched, demanding the resignation of the education minister and protesting against pay cuts and a steady deterioration in working conditions.
Unions said the government also plans to privatise many state schools and cut about 50,000 jobs to meet the conditions on bailout loans.
Union spokesman Mario Nogueira said that the plans, revealed in a recent International Monetary Fund document, would "mean the end of a free and inclusive public school system."
Portugal is headed for a third straight year of recession, and was given a €78bn (£66bn) loan from the EU and IMF in May 2011.
But the austerity conditions attached to the money have caused the jobless rate to soar to 16.3 per cent.
The cuts have proved to be highly damaging, triggering strikes and protests across Portugal.
The teachers' protest was the biggest so far this year.
The Portuguese have shown relative patience with the bailout terms but resistance has become more common as the economy continues to struggle.
And it could get worse when the largest tax rises in living memory start to be felt as workers receive their first pay cheques of 2013 at the end of the month.
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