The concept of the subject department is "fundamentally corrosive", Frank Lennon, headteacher of St Modan's High in Stirling, told the conference.
People built up professional identities based on their degrees, knowledge of their subject and their departments and often lost sight of children and their needs.
Mr Lennon, a member of the national review group on guidance which is due to report in the autumn, called for more focus on what it means to be a teacher in the 21st century.
Secondaries needed more teamwork to allow staff to become teachers of adolescents. "I'm sure you are all aware of the annual bout of schadenfreude when the physics department looks at the results of the maths department and goes, 'yes, same kids, we got better results', "There is something bizarre when you get that kind of routine response in the school and it is fundamentally about professional identity. They don't think of the needs of children.
"It's point scoring even on an individual pupil basis and I have been there as principal teacher of English for seven and a half years," Mr Lennon said.
He appealed for a systematic attempt to bring staff back into touch with the principles and values they set out with. People did not enter the profession to earn lots of money but to help young people develop.
Headteachers had to offer a vision based on values and principles that was an alternative to the corrosive effects of subject departments with their focus on relative ratings. The strength of a school should not be based on its performance in national examinations.