Abby Stevenson is struggling in math class. When she fails a math test, she tells Rachel Stevenson that her math teacher, Ms. Frost, didn't care, and Mrs. Stevenson comes to Stoneybrook Middle School to confront Ms. Frost, even though Abby didn't tell her mother the whole story. She later buys a study guide from Brad Simon but it turns out to be the actual test. Abby and four other students are suspended for three days, but Abby hides the notices of her suspension from her mother and spends Monday and Tuesday in the Stoneybrook Public Library. On Wednesday, however, she goes shopping and stops for lunch at Pizza Express, where she is caught by her mother. Starting Monday (two days after the twins' Bat Mitzvahs), Abby is grounded for a month with no sleepovers, no visits from friends, no phone privileges, and no parties (but she's still allowed to babysit and engage in her after-school activities).
On Thursday (after her suspension), she sees Mary Anne buying a similar "study guide" from Brad, and at the end of the school day, the two girls tell Ms. Frost about what happened. She believes them and apologizes for not believing Abby before. She also gives Abby the chance to retake the test after school next week.