Sarah, Duchess of York passed only two O-levels while at a top boarding school. The 64-year-old royal’s exam results were revealed after a slip detailing the outcome of the exams she took in June 1976 was found in a dusty filing cabinet, according to the Mail on Sunday. It appears to have been accidentally left behind at Hurst Lodge School in Ascot, where the duchess was a weekly boarder in the early 1970s, and shows she only passed spoken English, with an A, and art, with a C. Fees at the posh school were about £3,000 a year – equivalent to £21,000 a year today. The results also show Sarah go…