Fetish studio Severe Sex Films is set to release “Kink School: Extra Credit,” the next installment of their AVN- and XBIZ-nominated instructional series Kink School, through Exile Distribution. “‘Kink School: Extra Credit’ follows up on our Beginning and Intermediate BDSM instruction DVDs with sexy new skills for people who already know the basics,” explained Dee Severe, who co-directed with Jimmy…