The Baby-Sitters Club Wiki
The Baby-Sitters Club Wiki

Claudia and the Middle School Mystery is the 40th book in The Baby-Sitters Club series by Ann M. Martin.

Back Cover Summary[]

For once, Claudia's studied really really hard for her math test. And when Claudia gets her paper back, it has an A- on it. All right!

But then, Claudia's math teacher calls her to his desk and accuses her of copying off Shawna Riverson's test!

Claudia can't believe it. Neither can the Baby-sitters. Claudia would never cheat! And they're not going to rest until they help clear Claudia's name!


Claudia has actually studied for a math test. She feels like she did well. But another student makes the same grade while missing the same questions (and coming up with the same wrong answers). Claudia is accused of cheating on the test. The BSC helps clear her name.


When Stacey babysits for the Pikes, the triplets play baseball and a window breaks. They won’t confess who did it because they’ve decided to be like the Three Musketeers. Mrs. Pike grounds the boys until one of them confesses.


Claudia's Family

BSC Members





Pop Culture and Real-Life References[]

  • Princess Diana
  • The Three Musketeers
  • Ms. Frizzle and the Magic School Bus

Continuity and Inconsistencies[]



  • When they're trying to think of a way to trick Shawna into giving herself away, they mention how they set traps for Cokie in both of those mysteries and got her to give herself away. Actually, Cokie just made a revealing comment in both.
  • On page 94, Cokie's name is Cokie Gray when it should be Cokie Mason.
  • Claudia says that Mr. Zorzi doesn’t know her well. But in chapter one, she says she’s had him before and he knows that it takes her a while to catch up.

Ann M. Martin's Dear Reader Letter[]

Dear Reader:

As you can tell in Claudia and the Middle School Mystery, Claudia is not a great math student ... and neither was I. I squeaked through math. My grades were okay, but I had to work very hard to pass. Numbers just don’t make sense to me the way letters and words do. I was very embarrassed when my teachers suggested to my parents that they find a math tutor for me. But after I started working with my tutor and doing better, math wasn’t so bad anymore. My tutor was Johnny Valentine. He lived across the street from me. He was six years older, and I thought he knew everything. Guess what — Johnny used to be one of my baby-sitters.

As a baby-sitter, you can help your charges with their homework if they need it. If the kids are struggling, you can lend a helping hand. But remember, don’t do their homework for them; just show them how to do it themselves. They’ll really appreciate it, just like I appreciated the help Johnny gave me.


  • This is the first appearance of Shawna Riverson.
  • The working title for this book was Claudia and the Big Test [1].
  • Claudia is in a remedial math class.
  • This is the fourth time the triplets broke a window in the last three months.
  • The Kishi's have tacos for dinner in this book.
  • Claudia can always remember what she was wearing on any given day.
  • Some jobs taken but never see are Mallory at the Newtons, Jessi at the Braddocks, Stacey at the Johanssens, Claudia at the Perkins, and Kristy sitting for the Pikes (just four of them).
  • When she starts rhyming there's no stopping Vanessa.
  • Jessi teaches the Pike triplets "op talk."
  • This is the first time that Shawna ever cheated on any test.
  • Janine had a good relationship with the principal at SMS when she was going there.
  • In this book, only Claudia, Dawn, and Stacey are involved in the plan to search Shawna’s locker. But in book #17, when Claudia doesn’t want to go to the library to help with the research on witchcraft, Kristy says Claudia is going because the club sticks together.
  • Claudia isn’t allowed to take her test with her in chapter 5 because Mr. Zorzi needs it as evidence. But since she and Shawna missed the same problems in the same way, Shawna should’ve left her test with Mr. Zorzi as well (as further proof of the cheating).


Baby-Sitters Club Books
The Summer Before | #1 Kristy's Great Idea | #2 Claudia and the Phantom Phone Calls | #3 The Truth About Stacey | #4 Mary Anne Saves the Day | #5 Dawn and the Impossible Three | #6 Kristy's Big Day | #7 Claudia and Mean Janine | #8 Boy-Crazy Stacey | #9 The Ghost at Dawn's House | #10 Logan Likes Mary Anne! | #11 Kristy and the Snobs | #12 Claudia and the New Girl | #13 Good-bye Stacey, Good-bye | #14 Hello, Mallory | #15 Little Miss Stoneybrook... and Dawn | #16 Jessi's Secret Language | #17 Mary Anne's Bad-Luck Mystery | #18 Stacey's Mistake | #19 Claudia and the Bad Joke | #20 Kristy and the Walking Disaster | #21 Mallory and the Trouble with Twins | #22 Jessi Ramsey, Pet-sitter | #23 Dawn on the Coast | #24 Kristy and the Mother's Day Surprise | #25 Mary Anne and the Search for Tigger | #26 Claudia and the Sad Good-bye | #27 Jessi and the Superbrat | #28 Welcome Back, Stacey! | #29 Mallory and the Mystery Diary | #30 Mary Anne and the Great Romance | #31 Dawn's Wicked Stepsister | #32 Kristy and the Secret of Susan | #33 Claudia and the Great Search | #34 Mary Anne and Too Many Boys | #35 Stacey and the Mystery of Stoneybrook | #36 Jessi's Baby-Sitter | #37 Dawn and the Older Boy | #38 Kristy's Mystery Admirer | #39 Poor Mallory! | #40 Claudia and the Middle School Mystery | #41 Mary Anne vs. Logan | #42 Jessi and the Dance School Phantom | #43 Stacey's Emergency | #44 Dawn and the Big Sleepover | #45 Kristy and the Baby Parade | #46 Mary Anne Misses Logan | #47 Mallory on Strike | #48 Jessi's Wish | #49 Claudia and the Genius of Elm Street | #50 Dawn's Big Date | #51 Stacey's Ex-Best Friend | #52 Mary Anne + 2 Many Babies | #53 Kristy for President | #54 Mallory and the Dream Horse | #55 Jessi's Gold Medal | #56 Keep Out, Claudia! | #57 Dawn Saves the Planet | #58 Stacey's Choice | #59 Mallory Hates Boys (and Gym) | #60 Mary Anne's Makeover | #61 Jessi and the Awful Secret | #62 Kristy and the Worst Kid Ever | #63 Claudia's Freind Friend | #64 Dawn's Family Feud | #65 Stacey's Big Crush | #66 Maid Mary Anne | #67 Dawn's Big Move | #68 Jessi and the Bad Baby-sitter | #69 Get Well Soon, Mallory! | #70 Stacey and the Cheerleaders | #71 Claudia and the Perfect Boy | #72 Dawn and the We Love Kids Club | #73 Mary Anne and Miss Priss | #74 Kristy and the Copycat | #75 Jessi's Horrible Prank | #76 Stacey's Lie | #77 Dawn and Whitney, Friends Forever | #78 Claudia and Crazy Peaches | #79 Mary Anne Breaks the Rules | #80 Mallory Pike, No. 1 Fan | #81 Kristy and Mr. Mom | #82 Jessi and the Troublemaker | #83 Stacey vs. the BSC | #84 Dawn and the School Spirit War | #85 Claudia Kishi, Live From WSTO! | #86 Mary Anne and Camp BSC | #87 Stacey and the Bad Girls | #88 Farewell, Dawn | #89 Kristy and the Dirty Diapers | #90 Welcome to the BSC, Abby! | #91 Claudia and the First Thanksgiving | #92 Mallory's Christmas Wish | #93 Mary Anne and the Memory Garden | #94 Stacey McGill, Super Sitter | #95 Kristy + Bart = ? | #96 Abby's Lucky Thirteen | #97 Claudia and the World's Cutest Baby | #98 Dawn and Too Many Sitters | #99 Stacey's Broken Heart | #100 Kristy's Worst Idea | #101 Claudia Kishi, Middle School Dropout | #102 Mary Anne and the Little Princess | #103 Happy Holidays, Jessi | #104 Abby's Twin | #105 Stacey the Math Whiz | #106 Claudia, Queen of the Seventh Grade | #107 Mind Your Own Business, Kristy! | #108 Don't Give Up, Mallory! | #109 Mary Anne to the Rescue | #110 Abby the Bad Sport | #111 Stacey's Secret Friend | #112 Kristy and the Sister War | #113 Claudia Makes Up Her Mind | #114 The Secret Life of Mary Anne Spier | #115 Jessi's Big Break | #116 Abby and the Best Kid Ever | #117 Claudia and the Terrible Truth | #118 Kristy Thomas, Dog Trainer | #119 Stacey's Ex-Boyfriend | #120 Mary Anne and the Playground Fight | #121 Abby in Wonderland | #122 Kristy in Charge | #123 Claudia's Big Party | #124 Stacey McGill... Matchmaker? | #125 Mary Anne in the Middle | #126 The All-New Mallory Pike | #127 Abby's Un-Valentine | #128 Claudia and the Little Liar | #129 Kristy at Bat | #130 Stacey's Movie | #131 The Fire at Mary Anne's House
Super Specials
#1 Baby-sitters on Board! | #2 Baby-sitters' Summer Vacation | #3 Baby-sitters' Winter Vacation | #4 Baby-sitters' Island Adventure | #5 California Girls! | #6 New York, New York! | #7 Snowbound | #8 Baby-sitters at Shadow Lake | #9 Starring the Baby-sitters Club #10 Sea City, Here We Come! | #11 The Baby-sitters Remember | #12 Here Come the Bridesmaids! | #13 Aloha, Baby-sitters! | #14 BSC in the USA | #15 Baby-sitters' European Vacation
Portrait Collection
Stacey's Book | Claudia's Book | Dawn's Book | Mary Anne's Book | Kristy's Book | Abby's Book
The Baby-Sitters Club Notebook (1987) | The Baby-Sitters Club Postcard Book (1991) | Trivia & Puzzle Fun Book (1992) | Ann M. Martin: The Story of the author of the Baby-sitters Club (1993) | The Baby-Sitters Club Guide to Babysitting (1993) | The Baby-Sitters Club Chain Letter (1993) | The Baby-Sitters Club Secret Santa (1994) | Audio Books on Cassette Tape (1994-5) | BSC Movie Novelization (1995) | The Complete Guide to the Baby-Sitters Club (1996) | Autograph Book (1998) | BSC Graphic Novels (2006-present) | We Are the Baby-Sitters Club: Essays and Artwork from Grown-Up Readers (2021) | Welcome to Stoneybrook: A Guided Journal (2021) | The Official Coloring Book (2023)