A Delaware mother faces felony charges after police said she beat her 9-year-old son with an extension cord for taking a check from her checkbook to purchase a book at his school’s book fair.

According to Philadelphia NBC affiliate WCAU, Serena Wardlaw, 42, of New Castle, Del. was arrested and charged with four counts of second-degree assault and five counts of endangering a child.

The abuse was discovered by her son’s elementary school nurse, who notified authorities after she found wounds on both of the boy’s arms. An investigation later revealed that she struck the boy after he took the check to pay for the book.

Police also found that Wardlaw had previously struck her 7-year-old twin daughters. “Prior injury marks about their body that was consistent with being struck with the same object,” police told The Philadelphia Inquirer.

Wardlaw was released on $21,000 bail and was prohibited from having unsupervised contact with her children.