The teaching employers have criticised teaching unions for requesting a 5% pay rise this year.
The teaching employers include the Department of Education, the Education Authority and the Council for Catholic Maintained Schools.
In a statement, they said they did no see how the pay rise "could be met in the context of current legislation".
They also said the decision by some schools to reduce teaching hours would have a "real detrimental impact".
A secondary school in south Belfast had previously announced it would close to pupils at 13:00 GMT every Wednesday.
In their joint statement, they called for teachers to suspend current industrial action, which is described as "short of strike".
That has meant that many teachers have refused to attend meetings or take part in other activities after school hours.
"As a direct result of the action short of strike, some schools are reducing teaching time to allow teachers to complete other professional duties that would normally be completed outside class hours," they said.
"Less class time for pupils has a real detrimental impact on their educational experience.
"In that context, we are disappointed that the teaching unions have requested a 5% pay increase at this time."
The statement added: "Whilst we sympathise with all staff in the education sector whose salaries have not risen in line with inflation, we fail to see how a pay increase of 5% could be met in the context of the current budget situation."