Complex sentence: The plot consists of Polly's class going to Pollyworld to appear on a game show and a jealous classmate named Beth trying to help Polly's future stepmom get rid of Polly (specifically they are trying to send her to boarding school).
Split into simpler sentences: The plot consists of Polly's class going to Pollyworld to appear on a game show. Meanwhile, a jealous classmate named Beth tries to help Polly's future stepmother get rid of Polly (by sending her to boarding school).