Complex sentence: Tupou became widely known as a schoolboy rugby player in 2014 while playing for Auckland's Sacred Heart College First XV, when he became an internet sensation for his 3 tries against Kelston Boys High School.
Split into simpler sentences: Tupou became widely known as a schoolboy rugby player in 2014. While playing for Auckland's Sacred Heart College First XV, he became an internet sensation for his 3 tries against Kelston Boys High School.