Judith Mullen, new president of the Secondary Heads Association, said yesterday that she feared there would be "a generation of Spice babies born to teenage mothers".
She blamed Labour and Conservative governments for over-emphasising examination qualifications. "There are a lot of young women whose self-esteem has been knocked because they don't feel they have achieved the magic five A*-C grades at GCSE. For some, pregnancy might be a way of feeling success," she said.
Teenage pregnancies in Britain, she pointed out, were higher than in any other European country.
In the past decade national tests have been introduced for children aged 7, 11 and 14, and last week the Government announced details of assessments for all children when they begin primary school.
Heads have criticised government exam performance tables, which use top GCSE grades as their main measure, tempting schools to neglect their weakest pupils.
Mrs Mullen, who is warden of Melbourn Village College in South Cambridgeshire, said that girls who struggled at school and came from homes where they received little encouragement often suffered from lower self-esteem than boys who fell behind.
Heads were wholeheartedly behind the drive to raise standards but the emphasis on test and exam results meant guidance on careers and personal development was being squeezed out. "We have to get back to looking at the importance of personal development for young people."
She said that she was not "knocking" the Spice Girls, who were in their 20s and "as I understand it, in loving, caring relationships".
t Charles Clarke, the Schools minister, announced grants of pounds 150,000 yesterday for 20 projects that will pair youngsters with adult role models. The aim is to improve motivation and raise aspirations.
A project in Camden, north London, will centre on girls, mainly from ethnic minorities, who have low self-esteem or are underachieving. They will have successful businesswomen as mentors. A scheme in Tameside, Manchester, will provide the children of travellers with mentors.