Original paper headline: Secondary heads urged to federate in bid to cut costs
Karl Napieralla, director of education for Neath Port Talbot council, urged ASCL Cymru members to follow the example of the primary sector, which has used similar tactics to cope with reduced budgets.
Speaking at ASCL Cymru's annual conference, Mr Napieralla, also chairman of the ADEW (Association of Directors of Education in Wales), told heads: "I don't think you have looked realistically at the extent as to how you can pull efficiencies out of the system.
"In the primary sector they have some proven developments like sharing backroom staff that are making real inroads into efficiencies."
He warned that schools can become "complacent" about the amount of cuts they have made to their services, and said there are always more ways to save cash.
"There's no point saying we have done all we can do because there is always more to do," he said. "We have to be striving to be more effective because we have to exist in the real world. In future, there won't be as many resources to go around as there are now."
Although Mr Napieralla suggested that further demands for efficiency savings in schools were inevitable given recent financial forecasts, he said teaching unions in Wales should not give up fighting for equality of funding with other UK regions.
But Brian Lightman, headteacher of St Cyres School in Penarth, said it was "completely unrealistic" to suggest that school leaders could achieve anything more than the "most marginal" of further efficiencies. He said: "Local authorities and the Assembly government need to understand that any further cuts will lead to removal of frontline services in the classroom.
"If there are budget reductions we would like to hear what we are expected to stop doing and which aspects of our service local and central government would like us to discontinue."