Her boy toy may have been a stud, but he was no student. A Queens teacher fired for bedding a 17-year-old male model is suing to win her job back, saying she had no idea her lover boy was enrolled in high school during their affair. Gina Salamino, 37, contends her job as a tenured second-grade teacher at Public School 121 should have been spared because Joshua Walter was so busy catwalking he never attended a single class during the 2006-07 school year. "They have no case," Salamino angrily told the Daily News. "There is no improper relationship."Salamino maintains...