Justin Timberlake joins Bad Teacher March 3, 2010 JT is bringing sexy back… to middle school? Justin Timberlake has joined the cast of the forthcoming comedy Bad Teacher. According to reports, the singer will join Cameron Diaz and Jason Segal as a substitute teacher win the picture. Written by the Office team Lee Eisenberg and Gene Stupnitsky, the film centres around an unorthodox middle school teacher. Timberlake will next be seen in David Fincher’s Facebook thriller The Social Network.