ALMOST 1,100 teachers phoned in sick for between 90 and 260 days in the space of four years.
The level of absenteeism among some teachers has sparked hundreds of warning letters threatening to stop pay.
According to new figures from the Department of Education, some teachers at both primary and secondary level routinely take sick leave that can run for months.
"In the event of your continued absence, your entitlement to salary will expire on (specified date)," the letters warned.
The teachers were told that if there absence continued beyond 365 days their salary would be stopped.
It means teachers out sick for more than 260 days in four years have missed the equivalent of at least an entire school year in the period -- given that the primary school year lasts 183 days, while secondary schools open for 167 days.
Overall 669 primary teachers and 415 secondary teachers received the warning letters. It is not clear how many of them have actually been struck off the payroll. However, the department has confirmed 115 teachers are currently out on long-term sick leave with no pay because they have exceeded the sick leave limit.
Teachers can claim seven days of uncertified sick leave each year -- but must be certified as unfit to work by their doctors to qualify for sick pay after that.
But teacher unions maintain that the overall level of sick leave among teachers is low -- and that many teachers who were warned about their high sick leave last year had serious illnesses such as cancer, heart conditions and depression.
The 1,084 teachers who have received warning letters account for just 2pc of the 52,000 teachers working in primary and secondary schools.
Teachers who are on sick leave during weekends and school holidays also have this included in their sick leave tally. The department said this was "in line with civil service norms in counting sick absences".
A spokesman for INTO union said: "INTO case work files indicate that roughly half of teachers on long term sick leave are dealing with cancer diagnoses, treatment or recovery."
The current overall absence rates for primary teachers are 8 days and 7.4 days for secondary school teachers -- compared to 11.3 days in the civil service.
But a new policy put in place three years ago has led to a huge drop in uncertified sick leave taken by teachers.