Minister for Health Leo Varadkar has criticised secondary school teachers unions over their planned strike action and said the unions are holding up reform of the Junior Cycle.

Mr Varadkar said Minister for Education Jan O'Sullivan had made significant compromises in a bid to reach an agreement with teachers.

Up to 350,000 students will be affected by the closure of schools on Tuesday over opposition to the reforms.

Mr Varadkar said the closure of schools would not serve anyone.

One of the major issues over the reforms is the requirement for teachers to assess 40% of their own students' work for the exam that will replace the Junior Certificate.

Earlier this month, Ms O'Sullivan said she would not row back on the issue of external assessment.

She described the strike action as "disproportionate" and said she had "moved considerably" to address teachers' concerns.

Association of Secondary Teachers, Ireland president Philip Irwin said teachers were "at one" with the issue of external assessment and while the teachers were open to talks with the minister, external assessment is the standard they wanted to "stick with".