80s lover

Hi I have a question and I mean no disrespect at all bc I love this story and hope they both get a happy ending. 
          	  Billy works at a garage and he’s 20-21 yrs old? 
          	  But in the Nancy chapter he’s at school. 
          	  Am I missing something that I misunderstood his age or did he fail a lot? 
          	  I’m just trying to piece everything together. 
          	  I really do love this story. I always wanted him to be with her in show but the show had other plans. 
          	  Can’t wait for new chapters