THE Education Department's failure to pay up to three decades worth of after-hours call-out penalty rates to school administration staff could see some schools forced to find $200,000 in back pay.
Community and Public Sector Union branch secretary Tom Lynch confirmed the massive potential of the claims to impact on individual school budgets.
A dispute over the payments dates back to the end of 2008.
The average school, with up to five staff listed as after-hours on call, might have to find $100,000 - potentially $220 million - across Tasmania's 220 public schools.
The department, not the schools, should pay for the oversight, Mr Lynch said.
"I understand the department are at the end stage of considering the back pay claims.
"They are talking to principals about how (payment of substantiated claims) could be done."
Education Minister Lin Thorp said the matter was before arbitration and she would not comment.
Education Department deputy secretary Greg Glass said that the union lodged a dispute with the Tasmanian Industrial Commission in December 2008 in relation to the non-payment of availability allowances to school executive officers.
"Discussions have continued since that time with the CPSU with the aim of achieving an agreed outcome," he said.
"As part of that process, the department is currently having discussions with principals in relation to claims at their school."
Opposition education spokesman Michael Ferguson said that no payments should come from school budgets and that school resourcing must not be affected as a result of the claims.
The allowance has been part of the administration assistant award for more than 30 years.
Originally 80.7 cents an hour, in 2009 it rose to $2.30 an hour.
It was during the three-year negotiation between the union and the department for the increase that the union discovered the majority of public schools had never paid the allowance.
"At one school it's $200,000 for 32 years - it's an award entitlement that has not been paid," Mr Lynch said.
He could not say how many claims had been made or substantiated.
"It could end up being a lot of people. We have helped people put together evidence," he said.
Compiling evidence was easy because many of Tasmania's city and rural school administration staff had long-standing relationships with police and emergency services as the known after-hours point of contact, Mr Lynch said.
He said principals were concerned at the scale of the back pay amounts and believed that responsibility for the oversight should stay with the department.
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