Iranian teachers gathered in major cities including Tehran and Shiraz on Thursday to protest against low pay.
Over the course of the past few years teachers have often taken to the streets in protests over salaries and other problems.
Videos on social media showed teachers calling on each other to stand up against the injustice.
As some took to the streets, others stood outside schools with signs calling for change.
One of the chants heard in protests in Isfahan called for a release of teachers who have been imprisoned.
In December, a three-day protest and a strike that brought Iran's educational system to a standstill led to the nation's parliament passing emergency legislation to raise teachers' salaries.
The new legislation guaranteed that teachers would earn about 80 per cent of the salaries of university faculty members, fulfilling one of the protesters' demands. The law would ensure that teachers earn a minimum of about 80 million rials ($267) per month, if it was enacted, compared with an average of about 60 million rials currently paid to teachers.
The law that was finally approved is not new, having been introduced in Iran's parliament time and again and routinely rejected.
Despite the approval of the law, little has been done to put the legislation into effect and teachers have yet to see a rise in their salaries.
Iran is suffering with high unemployment, high inflation and a soaring poverty rate amid economic mismanagement and harsh US sanctions.