Angelina Jolie  and  Brad Pitt ’s son  Knox Jolie-Pitt went from cap and gown to gloves and kicks in the span of a few hours ... celebrating his high school graduation before stepping into the ring for a Muay Thai fight later that same night. The 17-year-old surprised classmates and parents during a graduation speech Friday in Los Angeles when he revealed he'd be competing after the ceremony. Knox even joked to the crowd that he was going to "knock 'em" out ... drawing cheers from the audience.