By Dan Warburton The Duchess of York passed just two O-levels despite attending an elite boarding school. Sarah Ferguson’s exam results have been found on a slip in a dusty old cabinet at her posh school. The 64-year-old was reported to have gained six O-levels at the school, where fees were about £3,000 a year – the equivalent of £21,000 a year today. But the newly uncovered document shows that the would-be Duchess gained an A in spoken English and a C in art. She got Ds in English language, English literature and biology, which then counted as a fail. She also failed French and geography. Sa…