Daniel McIlwaine, who taught at St Thomas Aquinas RC high in Chorlton-cum-Hardy, Manchester, was given a reprimand to remain on his record for two years.
The panel ruled that although he had not acted with dishonesty, Mr McIlwaine had breached expected standards of conduct.
Bradley Albuery, presenting officer, told the disciplinary hearing: "As a teacher with more than 30 years of experience he knew or should have known that papers should not be opened before an exam is set."
The panel heard Mr McIlwaine was asked to find out dates and times for an exam in 2003 and to tell parents and pupils. He went to the school's examinations officer who, he says, suggested opening exam papers to check.
Mr McIlwaine said he had asked if opening the papers was acceptable and was told it was. "The exams officer then told me the times and dates by shouting them from the annex," he said.
He admitted putting pressure on the exams officer but denied he had been involved in a security breach.
Two exam papers went missing but Mr McIlwaine, who now works part-time at a nearby school, said he was not responsible and this did not form part of the case.