The Education of Margot Sanchez by Lilliam Rivera
When Margot gets grounded, her parents make her work at the deli in their grocery store. Worried she's losing her carefully cultivated prep school reputation, Margot will do anything to make sure she's at the school's biggest beach party.
Review from School Library Journal:
Margot is disappointed to be spending her summer working in her family's Bronx-based chain of grocery stores, away from her elite prep school crowd. She is suffering the consequences of using her father's credit cards to finance her wardrobe and would much rather be partying with her friends and her crush in the Hamptons. Margot is rude to her family's employees, rejects her childhood friend, steals beer from her family to impress her new friends, and casually loses her virginity (to a guy who clearly doesn't value her much) after she's been drinking. Her attempts to redeem herself as she finally sees the error of her ways are effective, though, and over the course of the summer, Margot slowly learns the value of real friendship, navigates some family secrets, and begins to see her Puerto Rican heritage in a different light, culminating in an unsurprising but happy conclusion.