An Iranian teachers’ union on Monday issued a call for a nationwide closure of schools on Feb. 18, designating the day as one of mourning and protest in response to the killing of school students during recent unrest.

The Coordination Council of Iranian Teachers’ Trade Associations urged educators across the country to refrain from attending classrooms and administrative education offices, The Caspian Post reports, citing Iran International.

It also appealed to parents, asking them not to send their children to school on that day in solidarity with the protest action.

In an official statement, the umbrella organization - which connects teachers’ trade associations in multiple provinces - claimed that more than 230 children and teenagers had lost their lives at the hands of government forces amid the protests.

The union further encouraged teachers and members of the public to take part in 40th-day memorial ceremonies for those who were killed. It stressed that vacant seats in classrooms should not become a normal sight and emphasized that schools must stand as spaces where the fundamental right to life is defended and demanded.