A number of secondary schools have asked some children to stay at home and picket lines are expected at least three educational establishments.
The NASUWT general secretary does not believe the teaching union is being unrealistic.
Patrick Roach was at the front of the picket line this morning as some teachers downed tools outside St Ninian's High School.
It's in support of a row over pay and conditions.
He told Manx Radio he travelled from the UK because it was an important day for the teachers here.
He added government needs to address the pay and work crisis to improve the education system: