More than 1000 year 9 students across Northland went without lessons as teachers took the first step in a month-long series of proposed industrial action.
The Post Primary Teachers' Association - the union representing secondary school teachers and principals - announced last week it would take "rostering home action" which will see teachers opt not to teach a certain year group on a particular day, over four weeks.
It began yesterdaywith year 9 students and is scheduled to continue with Year 10 students on June 11, Year 11 on June 25 and Year 12 on July 12.
Ministry of Education figures for 2019 show there are 1770 year 9 students enrolled in schools in the Te Tai Tokerau region.
The industrial action comes after secondary school, primary school and area school teachers joined forces for a mega-strike last week.