Any idea what is the plot structure used in Bridge to Terabithia by Katherine Paterson?

The story opens as we are introduced to Jess, a boy who comes
from a poor family marked by conflict between the parents. As he goes to school, he is looking
forward to hopefully winning a race. However, the race is actually won by Leslie, a new girl who
started his school that day. Jess and Leslie form a friendship and play together in the woods,
forming a magical kingdom of Terabithia which they access by crossing a bridge over a river.
Their friendship deepens. However, tragedy strikes when Leslie dies in an accident when she tries
to cross the river to go to Terabithia herself. The way that Jess has to accept this truth and
come to terms with the end of his childhood marks the rest of the story, which finally ends when
he takes his little sister and introduces her to Terabithia.