Lea Michele, Chris Colfer, Cory Monteith to leave 'Glee'

Lea Michele, Cory Monteith and Chris Colfer will leave "Glee" after Season 3. (Fox)

Rachel, Kurt and Finn are graduating.

The "Glee" stars who play them, Lea Michele, Chris Colfer and Cory Monteith, "are not going to be back at all for Season 4," the show's creator Ryan Murphy told The Hollywood Reporter Wednesday.

"Glee" begins its third season Sept. 20 on Fox. Murphy said the decision had been taken in order to keep the high school musical comedy credible.

“You can keep them on the show for six years and people will criticize you for not being realistic,” he told the Hollywood Reporter, “or you can be really true to life and say when they started the show they were very clearly sophomores and they should graduate at the end of their senior year.”

Other characters also could be leaving the show when Season 3 comes to an end in May 2012, Murphy suggested. A major theme of the upcoming season will be the kids planning for life after high school.

Colfer, 21, has won and Emmy and Screen Actors Guild award for his portrayal as bullied gay teen Kurt on the show.

Fans have been flipping out for the past month since it was announced that Chord Overstreet, who plays Sam Evans on the series, has not been picked up as a series regular for Season 3. What’s going to happen now?