This lesson is taken from Teaching with Favorite 100th Day of School Books available from Scholastic Professional Books.

In 100 Days of Cool by Stuart J. Murphy, it’s the first day of school and the students in Mrs. Lopez’s class are dressed in anything but ordinary outfits. They’re wearing sequins, wild sunglasses, a big bow tie, lively patterns, eye-catching colors, and more. When Toby asks why, he finds out they’re planning on celebrating 100 days of cool. That’s “School!” he tells them, but it’s too late to change, and they’re on their way to finding 99 more ways to be the coolest class ever.

Meeting the Math Standards
Number & Operations:

• one-to-one correspondence
• recognize how many
• connect number words and numerals to the quantities they represent
• fractions
• computation
• number combinations
• estimation

Measurement:

• develop concepts of time and the way it is measured

Data Analysis & Probability:

• gather data
• sort and classify data according to attributes
• organize data
• represent data with objects, pictures, and graphs
• discuss events as likely or unlikely 

Before Reading
Cool! That’s a favorite word among children. Let children say the title aloud. Then play with the -ool word family as a warm-up to this book. What other words could take the place of cool in this title? There’s school, of course. But students will have fun substituting pool, toadstool, spool, uncool, preschool, and so on.

Send students on a calendar adventure to find out what day the 100th day of school is. Now add some fractions to the fun: What day will it be when students are 1/4 of the way to the 100th day? 1/2? 3/4? (Talk about how many days each of these fractions represents.)

After Reading
This book is full of invitations to have fun with math. Use the questions below to take the text and pictures further with a discussion that invites students to think about the relative position of whole numbers, commonly used fractions, grouping, and estimating.

• In the number line on pages 4–5, why is the number one bigger than the other numbers and red, while the other numbers are smaller and blue? (It lets the reader know what day of school it is.)
• Find the number line that shows the second day of school (pages 10–11). Where would you put Day 8 on this number line? Why?
• What place on the number line shows halfway to 100 days of cool? What are some ways you can tell?
• On Day 82 Toby says, “They still need almost 20 new ideas.” Is the actual number more than 20 or less than 20? How do you know?
• How many groups of 20 days are there in 100 days? (Ask this question a different way: “What number on the number line shows when children are 1/5 of the way there?”) “What other groups can you see on the number line?” 

More to the Story

• After reading this book, children will know the ways in which the students in Mrs. Lopez’s class were cool on days 1, 2, 5, 8, 10, 17, 21, 25, 33, 41, 49, 50, 75, 82, 99, and 100. But what about the other days? Let students add on to the story to come up with more ways to be cool.
• Reread the story, stopping to record the number for each day as it is mentioned.
• Together, count the number of days mentioned. (16 ) Ask, “If the students are celebrating 100 days of cool, how many other days did they do something to be cool?” Let students explain their strategies for answering this question. Students might count up from the total number of days (16), using tallies or manipulatives to keep track. They might subtract 16 from 100, or they might show an understanding of composing and decomposing numbers by breaking 16 into 10 and 6, then subtracting 10 from 100 to get 90 and 6 more to get 84.
• Give each child a copy of the Number Line (PDF) . Have children cut apart the number line strips and tape them together to make a number line that shows 0 to 100.
• Ask children to glue the left-hand edge of the number line to the top of a large sheet of drawing paper, positioned horizontally. Then they can fold up the number line along the taped sections so that it will fit on the paper, and clip it in place.
• Let children write a new part of the story, telling how the children are cool on one of the days not mentioned in the story. First have them write the number of the day in red on the number line, making it bigger than the other numbers. Then ask them to write a draft of their addition to the story on plain paper and write a final version on a copy of the Story Page (PDF) . Have children mount their stories on the paper with the number line and then illustrate them, using colors as bright as those in the book.
• Let children work together to arrange their pages in chronological order and bind together. Display the new parts of the story in order, along with a copy of the book.

Cool Kids

• Has Mrs. Lopez’s class inspired your students to team up and be “cool” for a day? Brainstorm ways your class could be cool for a day. Take a vote and then invite students to participate in a “Day of Cool.” With one day down, how many more days would students have to go to be cool for 10 days of school? 20? 30? 40? Continue, encouraging children to explain how they arrive at their answers (9, 19, 29, and so on). Use this pattern to reinforce counting by tens.

How Many to Go?

• Strengthen understanding of number relationships and combinations with an activity that embellishes the story with word bubbles.
• Reread the story, this time stopping at page 9 when Mrs. Lopez says “. . . only 99 more days.” Write the number sentence to go with Day 1 (1 + 99 = __ ) and let students solve it.
• Continue reading, paying attention to Day 2 (pages 10–11) and Toby’s word bubble that states “. . . 98 days to go.” Invite a volunteer to write the number sentence for Day 2: 2 + 98 = 100.
• Repeat this procedure for Days 1, 5, 8, 17, 21, 33, 41, 50, 75, and 99. Note that there are no word bubbles for these days to tell how many days there are to go, so invite students to make them. Draw word bubbles on large sticky notes. For each of the days mentioned, have students write a remark in Toby’s voice that indicates how many days to go—for example, for Day 5 they might write “Wow! What are you going to do for the next 95 days?” For each comment, have students write below the word bubble the matching number sentence, such as 5 + 95 = 100.
• Place the sticky notes on the corresponding pages and let students revisit the book to read their additions to the story.