South Wales’ own Jack Black is set to open his latest rock school in Cardiff this September.   Ben Tiffin, who already runs rock schools in Fairwater, Swansea and Llanelli, is launching a new session in Llanishen High School on September 9, teaching 7-18 year old’s how to play guitar, bass, drums and sing in a band.   “We opened the Rock Project Cardiff in Fairwater last year and have been blown away by the success of the school,” the…