Schools are being punished by the new inspection system for doing their best to educate pupils who are unlikely to do well in exams, Brian Rossiter believes.
They now have an extra incentive to exclude troublesome, less academic students so they do not drag down the school's CVA figure, said Mr Rossiter.
Mr Rossiter is head of Valley comprehensive, Worksop. Valley faces an "inadequate" verdict from inspectors because its CVA figures are significantly below the national average. The figure is 954, well below the national average of 1,000. Mr Rossiter therefore said that, when completing the "results" section of a self-evaluation form on his school, he had no option but to rate it as inadequate.
This meant, he said, the school is likely to be judged inadequate overall when next inspected, and given a notice to improve.
This is in stark contrast to his last Ofsted, in 2001, when it was said to be an effective school with very good leadership.
Mr Rossiter said: "The school will be judged inadequate, no matter how good our leadership is, because standards and achievement are the main categories we are judged on."
But Mr Rossiter said that part of the reason his figures looked poor was that he has 27 vulnerable Year 11 pupils, many of whom, he said, might have been excluded by other schools.
He said they were given access to work-related learning such as modern apprenticeships, rather than taking many conventional GCSEs or vocational exams.
One of these pupils is Scott Webber, 16, who Mr Rossiter said was a "success story" for the school, even though he will score hardly any GCSE points. Last year, he had been at risk of exclusion. So he was given a programme of study including work experience as a lorry mechanic, and is now about to be hired as an apprentice by a local firm.
Mr Rossiter said schools had always had incentives to exclude low-scoring pupils to make themselves look better in league tables. But the weight given to CVA by inspectors had increased this. He said: "I could raise our CVA by permanently excluding those 27 pupils.
"It would appear that because we are meeting their needs, we are being penalised. This makes me most angry."