With that information, and the medical exam and affidavit a star must complete some 30 days before the cameras roll, firms are able to assess the risk.
Exam league tables are to be expanded to show more information about the spread of a schools results, showing how the most and least able pupils are performing.
"What has precipitated the change is an increasing concern over the very variable performance of exam boards, " said a spokesman for the Independent Schools Council information service (Iscis).
Gareth Pierce, chief executive of WJEC, later told the MPs the information filmed by the Daily Telegraph regarding the "cycle" of exam questions - which topics would be set each year - was already in the public domain.