Schools are turning out "amoral" children because they are failing to teach them right from wrong, according to a leading headmaster.
Too much time in many state schools is spent on academic studies, leaving youngsters missing out on a rounded education, Richard Walden, chair of the Independent Schools Association (ISA) argued.
Speaking at the ISA's annual conference in Warwickshire, Mr Walden is expected to warn that teachers working in state schools are being "overwhelmed" by the pressure to get good results and this is distracting them from teaching pupils good values.
He says: "Schools are turning out too many amoral children because teachers cannot find the time to teach the difference between right and wrong."
Mr Walden, who is also head of Castle House School in Shropshire, claims: " Too many staff are overwhelmed by the pressure to achieve results.
"It seems that the only results that matter are those which have created added value in terms of raising a pupil's statistical level from one stage to the next, and parents are increasingly buying in to this notion.
"This focus on league tables and attainment levels distracts teachers and effectively disables them from providing children with a more rounded and enriching education - one that will give them the moral compass they need for life."
He suggests that private schools devote much of their time to extra-curricular activities, a wide curriculum and personal, social, health and economic (PSHE) education.
Learning good values allows students to "distinguish the good from the bad and the true from the false", Mr Walden says.
And he argues that fee-paying schools are very good at developing pupils' character.
" The very nature of our schools, with their respect for discipline and academic seriousness, sport and culture, citizenship and community, service, environmental awareness, spiritual life and personal responsibility, sends out into the world young people with emotional intelligence, developed moral understanding and a willingness to make a contribution to society," he says.
"These are not measureable by statistics or on inspectors' tick charts, but they are the qualities that employers want and the world as a whole needs."
Mr Walden goes on to say: " We cannot measure the growth of maturity in a young person grade by grade.
"It is not a linear progression anyway.
"It takes time, but if we hold our nerve as educators and as schools - and that may mean resisting the demands of parents who want quick-fix results, or the pressures of external statistical grading systems, not to mention the difficult financial situations that we can face - if we hold our nerve, we will continue to turn out well-rounded individuals who make a difference to society, as we have for many years."
Privately educated children do well in life not because they are from "elitist or privileged" backgrounds, he insists, but because they have received a "value-rich education, provided with love".
The ISA offers professional support to the headteachers of around 345 independent schools.