Ian McCann, from Aberdeen, said 5,000 days were lost to stress-related illness in Dundee last year, while 12 per cent of staff in Aberdeenshire expressed interest in voluntary severance.
"Look around your own authority and you could be talking about millions of pounds to cover the cost of illness," he said.
Mr McCann said stress led to mental andphysical illness. "Ask any teacher and they'll tell you about increasing stress in schools," he went on.
Elizabeth Quinn, Glasgow, who worked with children with severe behavioural difficulties for 23 years, said even nursery teachers were facing "serious difficulties" and appealed for class sizes of no more than 20 in the first three years of primary.
Rachel Martin, from Musselburgh, said: "If the teachers are stressed out of their skulls, they're not working to full performance and the children get a raw deal."