Complex sentence: Ja'mie King, a private school exchange student, immediately makes friends with the most popular girls at Summer Heights High, but it soon becomes obvious that her friendship is not genuine when the girls discover her poster that makes fun of "public school skanks".
Split into simpler sentences: Ja'mie King, a private school exchange student, immediately makes friends with the most popular girls at Summer Heights High. It becomes obvious, however, that her friendship is not genuine when her so-called friends discover a poster in which she has made fun of them, calling them "public school skanks".