A.P. Bio canceled again, this time at Peacock

The school bell has tolled for the final time on A.P. Bio.

Series creator Mike O'Brien announced Monday that the education-themed comedy won't be getting a fifth season at Peacock, which previously rescued the show from its cancellation on NBC after two seasons.

"I'm sad to announce that AP Bio will not be renewed for a 5th season," O'Brien tweeted. "But mostly I'm feeling grateful right now. To all the fans who watched the show and fought for it to come back after the cancellation! And to Peacock & UTV for giving us two more seasons after that!"

Vivian Zink/NBC Patton Oswalt and Glenn Howerton on 'A.P. Bio'

He added, "This show has been one of the best experiences of my life and that's because of the hundreds of hilarious, hard-working, positive people that were involved," then went on to thank myriad cast and crew members.

Peacock said in a statement to EW, "We were honored to be able to give fans two more seasons of this beloved, quirky comedy. We're grateful to creator Mike O'Brien for his out-of-the-box storytelling and for taking us on this journey with these characters at Whitlock High."

A.P. Bio starred It's Always Sunny in Philadelphia's Glenn Howerton as Jack Griffin, a disgraced Harvard philosophy instructor forced to return to his hometown of Toledo, Ohio, and teach advanced placement biology at a local high school. The cast also included Patton Oswalt, Aparna Brielle, Mary Sohn, Lyric Lewis, Jean Villepique, Jacob McCarthy, Paula Pell, and Tom Bennett.

Season 4 dropped Sept. 2, and all 42 episodes of the series will remain available to stream on Peacock.

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• A.P. Bio canceled after two seasons at NBC

• A.P. Bio gets a revived season 3 on NBCUniversal streaming service

• A.P. Bio review: A slightly stale but enjoyable enough network comedy