What is the theme of Ray Bradbury's "All Summer in a Day"?

Ray Bradbury's wonderful short story about children living
on Venus who are anticipating their first look at the sun explores the themes of
friendship and loneliness.
Margot is a newcomer to the colony on Venus, where it rains 365 days a year. The sun
only comes out for one hour every seven years, and Margot is the only child in the class
who has ever seen the sun, having spent her earlier years on Earth. The outcast of the
class, Margot's classmates are jealous of her because she remembers the sunshine and
because she may soon be returning to Earth. When they lock her in a closet, Margot
misses the beauty of the one hour of sun. The children realize afterward that her
descriptions of the sunshine were accurate, and they regret their decision to bar her
from this rare event.