Headteachers must learn to say no to unreasonable work demands, and instead of staying late in school, they should go home.
This overwhelming message - that heads must at times put themselves first as their work commitments soar - was delivered at the annual conference of the NAHT Cymru union in Swansea.
It was a rather sombre conference overall. There were predictions of funding cuts and redundancies as the global financial crisis deepened its stranglehold at a time when major initiatives, such as the play-led foundation phase for under-7s, were bedding down.
But there was also an air of rebellion with support for a call by Dr Chris Howard, the union's national vice-president, for an all-out refusal by heads to implement the school effectiveness framework. This is an Assembly government strategy aimed at narrowing the gap between Wales's best and worst-performing schools, but he said heads should call a halt if it brought "mountains of paperwork" with it.
In her inaugural speech, Cheryl Wheldon, the union's new president, implored colleagues to work fewer hours and delegate more.
Heads can work 60 hours a week, or more, according to the union's research, and that could also mean illegal hours in the classroom.
"We have to learn to prioritise, to delegate, and to know when it's time to go home. Perhaps we should just get better at saying no," said Ms Wheldon.
Anne Hovey, a regional officer, also reassured an audience of predominantly primary heads that it was OK to make a stand against the long-hours culture and pressure to meet targets.
"I've spent many years watching heads and deputies put up with being undermined and undervalued, and I have had enough of watching it," she said.
The general consensus is that teachers in Wales now have better conditions, thanks to the 2003 workforce agreement. But heads are bearing the brunt of school budgets that fail to stretch to cover for lessons, a result of teachers having more planning and preparation time. Add to that more administration and a head's working week is suddenly 50-plus hours.
Despite the results of a survey published by The TES last month revealing that many teachers in England and Wales were still not getting their entitlements under the agreement, heads in Wales believe it is being widely enforced. Ms Wheldon, who is also head of Coedffranc Primary School in Neath Port Talbot, said the biggest challenge facing heads was undoubtedly the workload.
"Our work-life balance has deteriorated and there does not appear to be any let-up in the stream of initiatives coming our way," she said.
"The time to improve the management of our workload is now. We owe it to ourselves. If the workload is not going to change, the way we handle it must.
"We are so busy making sure that the needs of staff, pupils, parents, governors and local education authorities are met, we don't stop to think of ourselves until it's too late."
Unrealistic timetables, under-funding and a lack of trust were all hampering heads in their stressful roles, said Ms Wheldon.
Dr Howard told delegates: "The next few years are going to be difficult. Life is not going to be easy. We are going to be asked to do more and more with less and less."
But the seriousness of this year's conference, under the headline of "Challenge and Change", was interspersed with lighter and "inspirational" moments provided by renditions of traditional Welsh history and poetry, courtesy of two special guests - the author and scholar Hywel Teifi Edwards and the Eisteddfod chair-winning poet Mererid Hopwood.
Delegates were treated to a passionate Welsh history lesson by Mr Edwards. He thanked heads for all their hard work and recalled the time of the Treachery of the Blue Books, a period in Welsh 19th-century history when there was Welsh outrage following a report, written by mostly English contributors, which criticised the state of Welsh education and blamed it on the Welsh language and religious non-conformity.
Mererid Hopwood, the former children's poet laureate, also led poetry workshops.