Three of the biggest stars on hit musical TV comedy "Glee" will "graduate" high school next year and won't be back on the show for a fourth season in 2012, the show's creator said on Wednesday.

In an interview with showbusiness website The Hollywood Reporter, Ryan Murphy said that Lea Michele (Rachel), Chris Colfer (Kurt) and Cory Monteith (Finn) "are not going to be back at all for Season 4."

Murphy said the decision had been taken in order to keep the dark comedy, which features a group of misfits in a struggling high school choir, more credible.

"You can keep them on the show for six years and people will criticize you for not being realistic, 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," he told the Hollywood Reporter.

Broadcaster Fox could not immediately be reached for comment.

Murphy suggested that other characters would also be leaving the show when season three comes to an end in May 2012. He said that planning for life after high school will be a major theme of the upcoming third season of the Emmy-award winning show, which starts on September 20.

Colfer, 21, who plays a bullied gay teen on the Fox show, has won Emmy and Screen Actors Guild awards for his performance.

Both Colfer and the "Glee" series are expected to feature strongly in nominations to be announced on Thursday for the 2011 Primetime Emmy Awards -- the highest honors in the television industry.

"Glee" has become a pop culture phenomenon since its debut in 2009, propelling its young stars to red carpet fame, producing several hit albums of songs used in the show and spawning two nationwide concert tours by cast members.