Siptu today presented evidence at an Oireachtas education committee that it said illustrated the raw deal that school caretakers are suffering.
The union said research carried out by it found "major anomalies" between school caretakers employed by the Department of Education and those employed through Board of Management structures.
Among the findings, the survey revealed that one caretaker was earning as little as €7.55c, which is illegal, that many others were on the statutory minimum wage of €8.65c; and that 80 per cent of school caretakers employed under boards of management have no access to sick pay.
The research also found just 24 per cent have access to a pension scheme; 7 per cent have to pay their own private pension without any contribution from the employer; and that 79 per cent of caretakers do not receive premium or overtime payments for extra hours worked.
Siptu pointed out that school caretakers do not have access to national pay agreement increases, nor do they have incremental pay scales like their counterparts in community and comprehensive Schools.
Siptu organiser Sharon Cregan told the committee: "The underlying issue here is lack of funding for the education sector, particularly for people employed as ancillary staff such as caretakers and secretaries."