Independent schools that charge high fees are spending the money on reducing class sizes to keep parents happy, rather than focusing on more effective ways of improving results, new research suggests.
The schools spend their income on hiring more teachers rather than hiring better teachers, despite the fact that increasing staff numbers has not been shown to have a significant impact on attainment, according to the study.
Researchers from Birmingham and Bristol universities looked at financial and academic data for 348 independent schools, and specifically at the education provided for students aged 16-18. The sample comprises roughly two-thirds of the total number of independent schools catering for this age range.
"There's a huge range in fees and also in total school income," said Peter Davies of the University of Birmingham, who conducted the research. "So that raises the question: what do the schools with more money do with it?"
He and his colleague found that schools with higher fees employed more teachers and support staff per student than those with lower fees. The schools with high incomes did not, however, pay their staff significantly more than other schools did.
A school that charged 10 per cent more in fees than another school would typically spend 3.6 per cent of that extra income on hiring more teachers. A further 8.3 per cent would be spent on recruiting more support staff. Only 1.9 per cent of the additional income would be used on wage increases.
"They're not using their money to try to attract better teachers, which you might have expected," said Professor Davies. "These schools really wanted to please the parents. And the way you please the parents is by having smaller classes, regardless of whether it makes a difference to attainment."
Evidence shows that smaller class sizes make relatively little difference to attainment. By contrast, research has repeatedly concluded that hiring good teachers - often by tempting them with high wages - has a significant effect on achievement.
"We might imagine that parents are interested in smaller classes, whatever the research says," said Professor Davies. "Parents like them, so they're willing to pay for them."
Evidence does, however, show that schools with high fees tend to have impressive value-added results. This might be because they attract parents with high ambitions for their children, Professor Davies said, or because more money is devoted to teacher training and development.
But Barnaby Lenon, chair of the Independent Schools Council, said schools did not hire additional teachers purely in order to reduce class sizes. "Many staff are employed to run things outside the classroom, such as sport," he added. "Often they teach additional subjects, such as Mandarin or Arabic. Teachers do not come to work in independent schools because of salaries - they come because of good discipline and high standards."
Private school fees have risen considerably over the past decade, with boarding schools offering an array of top-class facilities often charging in excess of pound;30,000 a year.
Professor Davies believes that the research, which appears in the latest issue of the British Educational Research Journal, raises questions about whether state schools should be encouraged to function more like independent schools.
"If you give schools loads of money, and freedom over how to spend that money, they would not be spending it in a way that's most known to raise students' achievement," he said.
Bernard Trafford, head of the Royal Grammar School in Newcastle upon Tyne, agreed that parents were keen to see smaller class sizes. But he questioned the assumption that it was difficult to recruit good teachers without offering high salaries.
"It helps to encourage the teacher I want that we pay a competitive rate," he said. "But I don't have to make generous financial offers to get people to come and work in my school. We just make sure we pay them quite well. It's really about advertising well, making the job seem attractive. I don't call that a salary war."