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Lists

Ninth graders store many values in one variable with a list. Some operations change the list (append, remove, sort); others just read it (len, indexing, in). They sort operations by whether they change the list, then build and process a list.

Grade 9Lists55 minutes1 class periodCSTA / ISTEExplicit teaching4 StandardsCSTA
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Lesson at a Glance

Everything you need before the bell rings

Learning Objectives

Students will be able to…

  • ✓Create and index a list.
  • ✓Tell changing from reading operations.
  • ✓Add, remove & sort items.
  • ✓Loop over a list.
Essential Question

How do programs store and work with many values at once?

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Lesson Phases
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Vocabulary Terms
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Standards Aligned
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Interactive Task
Sort It · Interactive

Changes the List, or Just Reads It?

Project this and sort each list operation into Changes the list or Reads it (no change).

📋 Sort each — does it change the list or just read it?Try it
✏️ Changes the list
👀 Reads it (no change)
Tap an operation, then tap a box.
The Lesson · Use → Modify → Create (a coding progression with Unplugged practice)

55 minutes, five moves

Tap any phase to open the teacher moves and student actions.

1

Hook — One Box, Many Values

6 min

How would you store 30 names in code?

👩‍🏫 Teacher Moves

  • Show 30 separate variables.
  • Ask for a better way.
  • Set the goal.

🎒 Student Actions

  • Look.
  • Guess.
  • Get ready.
2

Use — Lists

13 min

Students use lists.

👩‍🏫 Teacher Moves

  • Send students to Changes or Reads?
  • Sort each operation.
  • Note changing vs reading.

🎒 Student Actions

  • Sort.
  • Say.
  • Note it.
3

Modify — Modify the List

14 min

Students modify.

👩‍🏫 Teacher Moves

  • Append then remove an item.
  • Sort the list.
  • Index the 2nd item.

🎒 Student Actions

  • Append.
  • Sort.
  • Index.
4

Create — Build

15 min

Students create.

👩‍🏫 Teacher Moves

  • Make a list of 5 items.
  • Add one and remove one.
  • Loop over it and print each.

🎒 Student Actions

  • Make.
  • Edit.
  • Loop.
5

Reflect — Reflect

7 min

Students close.

👩‍🏫 Teacher Moves

  • Name a changing operation.
  • Name a reading operation.
  • Complete the exit ticket.

🎒 Student Actions

  • Name one.
  • Name one.
  • Complete the exit ticket.
Standards Alignment

Built to the standards you report on

Aligned to the CSTA K-12 Computer Science Standards and the ISTE Standards for Students.

CSTA
3A-AP-13

Create prototypes that use lists to solve problems.

CSTA
3A-AP-16

Combine control structures with data to express ideas.

CSTA
3A-AP-21

Evaluate and refine computational artifacts.

ISTE
5 Computational Thinker

Organize data to build solutions.

Differentiation

One lesson, every learner

Multilingual Learners

ELL / EMERGING READERS
  • Use a numbered row of boxes.
  • Label index positions.
  • Act out append/remove.

Support & Access

IEP / 504
  • Use a 3-item list.
  • Index the first item only.
  • One operation at a time.

Stretch & Extend

GIFTED / EARLY FINISHERS
  • Use 2D lists (a grid).
  • Sort with a key.
  • Build a list from user input.
Materials

What to gather

  • 📽️Screen / board
  • 📋Operation cards
  • 💻Changes or Reads?
  • 🐍Python / editor
  • 📓Notebooks
  • 🎫Exit-ticket slips
Vocabulary

Key terms — hover for a quick definition

listan ordered collection of valueselementone item in a listindexan item position (starting at 0)appendadd an item to the endremovedelete an itemsortput items in orderlengthhow many items (len)mutablea list can be changed in place
Evaluate

Exit Ticket

Preview the three formative checks. Tap “Sample answer” to see what mastery looks like — hide them before you print for students.

QUESTION 1
Does append() change the list or just read it?
It changes the list (adds an item).
QUESTION 2
Does len(list) change the list?
No — it only reads how many items.
QUESTION 3
What index is the first list item?
0.

Reflect: lists.

Have students build a 5-item list, then add one and remove one. A printable lists worksheet is in the Computer Science library.

Study · Flashcards

Study the key terms

Tap a card to flip it, then rate whether you knew it. Built from this lesson’s vocabulary.

🃏 CS Lists (Grade 9)Flip
Card 1
Term
Tap to flip →
Meaning
0

Nice work!

Practice · Quiz

Check your understanding

A quick self-check with instant feedback, drawn from this lesson’s key terms.

📝 CS Lists (Grade 9)Quiz
Score: 0
1 / 6
Question 1
0%

Nice work!

Practice · Worksheet

Printable worksheet

A print-and-go review sheet with a built-in answer key. Tap “Show answer key” to reveal answers, or print the clean version for students.

🖨️ CS Lists (Grade 9)Print
Name: ________________________
Date: ____________

Part A · Write the word that matches each meaning

Word bank: append, element, index, length, list, mutable, remove, sort
  1. add an item to the end
  2. delete an item
  3. one item in a list
  4. an ordered collection of values
  5. a list can be changed in place
  6. an item position (starting at 0)
  7. how many items (len)
  8. put items in order

Part B · Show what you learned

  1. Does append() change the list or just read it?
  2. Does len(list) change the list?
  3. What index is the first list item?
Answer key — Part A: 1) append · 2) remove · 3) element · 4) list · 5) mutable · 6) index · 7) length · 8) sort
Part B: 1) It changes the list (adds an item). 2) No — it only reads how many items. 3) 0.