Schools need to upgrade their furniture because today's children have outgrown the tables and chairs designed to meet the needs of 1960s pupils, experts said yesterday. Pupils are generally so much bigger - in height as well as girth - that many no longer fit into standard school furniture.

The recommendation is made in a report from the British Educational Suppliers Association, backed by the former education secretary Charles Clarke, which warns that a generation of children could suffer from back problems as the result of squeezing into ill-fitting furniture for hours every day.

Dominic Savage, director general of Besa, said children were significantly taller now but obesity also contributed to the need for more ergonomic furniture in schools. He said: "Although our starting point was not a question of obesity, when we looked the average child today is very different to a child in the 1960s, which is the last time children were actually measured for determining measures of furniture."

A study of 1,500 children found significant variation in their sizes, Besa said. "Not only were children generally taller than their peers in the 1960s, but the range of heights in any age cohort was far greater." In addition, "the ratios of body to leg and arm lengths were different, meaning that accepted relative heights of chairs and tables were inappropriate," the report concludes. "All of this data supported the belief that our children are likely to be spending thousands of hours of their school lives on chairs and at desks and tables where their posture is poor and the potential for damage to backs is great."

Clarke said environmental and health standards had changed dramatically in the past 10 to 15 years. He added that more comfortable tables and chairs would be "better for the child as they grow up, as well as for the school and education".