Complex sentence: The school became well known when its choir for older pupils took part in the UK TV channel BBC 1's "Last Choir Standing" in 2008, going through auditions, callbacks, and knock out rounds.
Split into simpler sentences: The school became well known when its choir for older pupils took part in the UK TV channel BBC 1's "Last Choir Standing" show in 2008. The students went through auditions, callbacks, and knock out rounds.