Complex sentence: At school, Matilda befriends her teacher, Miss Jennifer Honey, who, astonished by Matilda's intellectual abilities, tries to move her into a higher class, but is refused by headmistress Miss Agatha Trunchbull.
Split into simpler sentences: At school, Matilda befriends her teacher, Miss Jennifer Honey, who was astonished by Matilda's intellectual abilities. She tries to move her into a higher class, but is refused by her headmistress Miss Agatha Trunchbull.