Little girls lie, older boys cry for their mothers, and adults are as immature as children in Aryn Kyle’s unflinching new collection.

Mean girls populate most of the 11 short stories, from a pair of fourth-grade tormentors named Megan to the star of a high school play who abuses her understudy — and her lovesick drama teacher.

The penetrating tales rarely evoke sympathy. But Kyle, author of the novel “The God of Animals,” covers so much emotional territory in the few pages of each story that her characters’ flaws are easily understood, if not forgiven.

In “Nine,” that lying little girl is about to have a birthday, and “after nearly nine years in this world, she knows that some things need to be worried about.” After all: “Tess’s mother left two years ago, and her red raincoat is still hanging in the front closet.”

Tess will not wear a new dress to school on her birthday, and she will not offer cookies or cupcakes to the other kids. Her father doesn’t realize what is supposed to happen on birthdays. His girlfriend doesn’t remember the birthday at all, and Tess is too busy trying to avoid humiliation to speak up when she should.

“Captain”s Club,” about tender seventh-grader Tommy Whittaker, is the collection’s saddest, sweetest story. Tommy “was not best friends with CJ Franklin, not any kind of friends, really” but still ended up on a Mediterranean cruise with CJ, his dad and dad’s girlfriend, Tree.

Tommy cries upon leaving his recently single mother, who bought him shorts and sunblock and a camera despite not having the money, and who gave him a $20 bill so he could buy his younger sisters a present.

“A wave of anguish washed through him as he realized that he had not brought money to buy a gift for his mother.” We know his sensitive heart is doomed to break, not just on this trip but again and again.

In “Brides,” drama queen Dilly Morris exploits the weaknesses and hopes of everyone around her to reach a finale that is telegraphed from the beginning but still a surprise. In “Allegiance,” a girl raised in Britain starts an American school as an outcast but soon calculates the price she’ll be forced to pay to fit in with the cool girls.

While most of the stories are full of angst, Kyle writes with a poignancy that keeps them from being unbearable. As a bonus, she’s darkly funny.

“He is proud that our store is ranked first in cleanliness for our region, which I guess is good since it’s ranked last in sales,” says a woman of her boss and married lover in “Sex Scenes from a Chain Bookstore.”

Only a few of the stories fail to resonate. Weakest is “Femme,” a manifesto of sorts about women who plunder their so-called friends’ lives. “We watch while you talk, catching the weaknesses in your expression, the moments your eyes dart sideways or your lips quiver.”

What Kyle does best — and, lucky for her readers, frequently — is parachute into ordinary, miserable lives and use her extraordinary talent to render them unforgettable.