SICK days at a troubled west Belfast school were nowhere near as high as reported by inspectors, it has been claimed.
An inspection report published in January found that staff at De La Salle College were absent an average of almost 40 days - almost five times the average absence rate for post-primary schools.
The INTO union has consistently challenged the figure of 39.6 days per teacher contained in the Education and Training Inspectorate's (ETI) published report.
Now, a separate document written by ETI, and seen by the Irish News, shows a significantly lower number of days lost due to illness.
It shows that in the 2015/16 financial year, an average of 18.1 days were lost.
The figure of 39.6 published by ETI, and disputed by unions and teachers, covered the 2015/16 academic year.
It has been claimed that, given the overlap between financial and academic year, that every member of teaching staff would have to have missed 24 days between March and June 2016 for the figure of 39.6 to be accurate.
It has been cautioned, however, that the absence rates for the 2016/17 financial year, which would also include part of the period covered by the 39.6 reported days, are not yet known.
A spokeswoman for ETI said the 39.6 was "the average calculated, provided and verified by the school".
"It is an average based on the total number of days absent owing to sickness as a percentage of the total number of days in the academic year 2015-16 which runs 1 September to 31 August. The 18.1 figure covers the financial year 1 April to 31 March. They are two different averages calculated from different data sets with different date ranges," she said.
The Irish News reported this week that the school is to hold preliminary disciplinary investigations relating to a letter signed by 31 teachers.
The letter is understood to have been critical of inspectors as well as the acting-principal and vice-principal.
Governors responded earlier this year by writing to teachers asking them to consider their positions.
Now, the governors have established an investigation panel "to investigate matters relating to potential serious or gross misconduct".
INTO northern secretary Gerry Murphy said the investigatory process was a matter that could only be resolved by the school authorities, the individual teachers and their trade union representatives.
"INTO has previously challenged the figures quoted in respect to staff attendance and totally rejects the assertion directed at teachers that they were involved in a `rolling sick day protest'," Mr Murphy said.
"INTO members in La Salle have been working tirelessly to ensure that the pupils are provided with the best education possible in these difficult times. They remain focused and committed to resolving the outstanding issues in the school."
