Large secondaries with sixth forms said they each face an annual exam bill of pound;130,000, a survey by the Secondary Heads Association found. A 900-pupil secondary without a sixth form can spend almost pound;70,000.
John Dunford, the association's general secretary, said pupils sit 30 million papers a year and that the system is at bursting point.
"Exams have become the master of education, not the servant," he said.
"External exams have assumed too much importance in the system."
Mr Dunford said schools and colleges spend too much time preparing for and conducting exams, and that the burden on teachers and pupils is greater than that in other countries.
He called for greater reliance on in-course assessment of pupils by teachers, a proposal backed by Mike Tomlinson, the former chief inspector who is reporting on the future of 14-19 education.
Mr Dunford said a new grade of teacher, known as a "chartered examiner", should be created to reassure the public that this would not lead to a drop in standards.
Chartered examiners would be experienced teachers accredited to carry out and oversee assessment which contributed to external exam results. Each large subject department in a secondary school would be expected to have at least one such teacher, he said.
The results of an investigation by consultants PricewaterhouseCoopers into exam costs are not expected before the end of the year.
Details of SHA's survey were published at a press conference to announce that Tim Andrew, head of a Buckinghamshire grammar school, will be the union's president for 2004-05.
Mr Andrew, head of Chesham high school, and Mr Dunford set out the union's priorities. These include moving away from the benchmark of five A*-C grade GCSEs as the main performance indicator for secondaries, and ensuring that increased collaboration between schools is not undermined by the Government's desire to hold each institution accountable for its own performance.
But rather than take on ministers in a public fight, the union plans to continue working closely with the Government, and believes that this is more likely to benefit its members.
Next month, SHA will publish a joint report with the Headmasters' and Headmistresses' Conference and the Girls' Schools Association setting out plans to move towards allowing students to apply for university places after they receive their A-level results.
A move towards such an admissions system is believed to have the backing of Charles Clarke, the Education Secretary.