Sudoku lesson plan for grades 2 to 5

Learning goals

By the end of the lesson, a student should be able to:

• Explain why a digit must go in a particular cell, using the row, column or box as the reason.
• Complete a 4x4 grid without repeating a digit in any row, column or box.
• Describe one step of a partner's solution out loud, in their own words.

Standards

This lesson supports three of the Common Core Standards for Mathematical Practice: MP1, make sense of problems and persevere in solving them, MP3, construct viable arguments and critique the reasoning of others, and MP7, look for and make use of structure. A student working through a Sudoku grid is doing all three at once, checking a claim against fixed rules, defending a move to a partner, and noticing patterns in rows, columns and boxes.

For UK classes, the same lesson fits the reasoning and problem solving strand of the KS1 and KS2 maths programme of study.

Lesson steps

Timings below add up to the full 45 minutes. Adjust the paired practice block if your class needs more or less time to settle into the pattern.

1. 5 min Warm-up. Draw a blank 4x4 grid on the board and fill in six or seven digits, leaving the rest empty. Ask the whole class to call out digits that must go in specific cells, and write them in as students explain their reasoning.
2. 5 min The three rules, in kid language. Every row gets the digits 1 to 4, once each. Every column gets the digits 1 to 4, once each. Every 2 by 2 box gets the digits 1 to 4, once each. Keep it that plain, then point to one row, one column and one box on the board grid so students see all three at once.
3. 10 min Guided solve together. Start a fresh grid on the board and solve it as a class, calling on different students for each move. Keep the questions specific rather than open ended, for example: "Which row has only one empty cell?", "Look at column 3. Which digit is missing?", "This box already has three digits. What does that leave?", "Why can't a 2 go in that cell?"
4. 10 min Paired practice. Pairs work through one 4x4 puzzle from the worksheet, talking through each move before writing it down. Circulate and listen for students solving by guessing rather than reasoning, and redirect them with one of the prompts above.
5. 5 min Independent 6x6 for early finishers. A pair that finishes its 4x4 puzzle correctly moves on to one 6x6 puzzle alone, working independently rather than waiting for the rest of the class.
6. 5 min Share-out. Pick two or three students to come to the board grid and explain one move each, naming the row, column or box that told them where a digit had to go.
7. 5 min Exit ticket. Students fill in the two blanks on the small grid below and hand in the sheet on their way out.

Exit ticket

Print or copy this small 4x4 grid onto the bottom of the worksheet, or hand it out separately. Two cells are blank. Each one has exactly one correct digit.

Differentiation

Support: write two or three extra digits into their 4x4 sheet before the lesson, so fewer cells need reasoning, and keep them paired with a partner rather than working alone.

Stretch: move a confident pair onto the easy 9x9 worksheet, then point them to the guided first puzzle online, which explains a full 9x9 grid one move at a time. Students who finish everything with time to spare can try Killer Sudoku, which keeps the same three rules and adds cages with a target sum.

Common misconceptions

Three habits come up often the first time a class meets Sudoku.

• Adding the numbers up. Some students treat the grid as a sum. Tell them the digits are just symbols, and letters or colors would work exactly the same way.
• Guessing when stuck. A student writes a digit in without a reason, then erases it later. Ask them to find a cell where only one digit fits before writing anything down.
• Expecting a diagonal rule. Some students assume the two long diagonals need the digits 1 to 4 as well. In classic Sudoku they do not. Only rows, columns and boxes are checked.

Follow-up ideas

Keep a weekly puzzle slot going after this lesson, using a fresh page from the monthly Sudoku pack each time. Students who want the rules written down between lessons can read the Sudoku rules page, which covers the same three rules on a full 9x9 grid with diagrams.

Materials

All three worksheet sets used in this lesson are free to photocopy for your own classroom. Each PDF ends with a full answer key.

• Starter 4x4 set (24 puzzles, 6 pages): A4 PDF or US Letter PDF.
• Junior 6x6 set (20 puzzles, 8 pages): A4 PDF or US Letter PDF.
• Easy 9x9 set for stretch students (16 puzzles, 10 pages): A4 PDF or US Letter PDF.

Free to print and photocopy for classroom use. Read the one-paragraph licence for the small print.