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ESL Lesson Plan · CEFR B2

Modals of Deduction ESL Lesson Plan (B2, 60 Minutes)

A complete 60-minute B2 lesson on Modals of Deduction, built round the theme "The Missing Student".

  • CEFR B2
  • 60 minutes
  • Teenagers and adults
  • Grammar
  • Modal Verbs
  • Modals of Deduction

About this lesson

Who it is for. Upper-intermediate students who use must and might for present deduction but say He mustn't be at home (meaning can't) and She must have went.

Everything the lesson needs is on this page: the language analysis, the timed stages with the teacher's own words and instruction-checking questions, the differentiation, the printable handouts and the answer key.

At a glance

Level
CEFR B2 (Upper-intermediate)
Learners
Teenagers and adults
Length
60 minutes. For 45 minutes, run "Freer practice" once through without the second round and cut "Feedback and wrap-up" to board-based error correction.
Skills
Speaking and writing
Language focus
Grammar: Modals of Deduction (must, might, can't – present and past)
Framework
PPP (presentation, practice, production)
Materials
Handout 1 (the mystery scenario), Handout 2 (certainty scale and practice), Handout 3 (clue cards), close-up photos of everyday objects (or descriptions).
Preparation
About 10 minutes: print Handouts 1 to 3, one per learner, and read the language analysis. The answer key is for you, not the class.

Aims

Main aim. To present and practise modals of deduction for present and past situations: must, might / may / could, can't / couldn't + base verb / be + -ing / have + past participle.

Learning outcome. By the end of the lesson, students can solve a mystery by making and justifying deductions about present and past events.

  • Subsidiary aim. To develop fluency in speculating and reasoning.
  • Subsidiary aim. To practise connected speech in must have /ˈmʌstəv/.

Language analysis

What to know before the lesson: the meaning, form and pronunciation of the target language, and the problems learners usually have with it.

Form and certainty

CertaintyPresentPresent continuousPast
~100% sure it's trueHe must be at home.She must be sleeping.They must have left early.
possibleIt might / may / could be him.He might be working.She might / may / could have forgotten.
~100% sure it's not trueIt can't be Ravi.They can't be playing outside.He can't / couldn't have seen us.

Accuracy points

  • Negative deduction is can't, not mustn't: He can't be at home (not He mustn't be at home).
  • Past: modal + have + past participle: must have gone (not must have went).
  • couldn't have and can't have are both used for the past.

Pronunciation

  • Weak have: must have /ˈmʌstəv/, might have /ˈmaɪtəv/, can't have /ˈkɑːntəv/.

Concept-checking questions

  • The lights are off. They must be out. Am I sure? (Almost sure.) Why? (The lights are off: evidence.)
  • He can't have seen us. He didn't say hello. Am I sure he didn't see us? (Almost sure.) · Is it about the past or now? (The past.)

Anticipated problems and solutions

ProblemSolution
mustn't for negative deduction.Board the certainty scale: must ↔ can't.
must have wentDrill past participles; error correction in practice.
Hearing of instead of have (must of).Show weak /əv/ is written have.
Deductions without evidence.Require because + evidence in the freer task.

Board plan

Left: vocabularyCentre: certainty scaleRight: pronunciation
evidence · clue · theory · suspect · disappear · alibi
100% YES: must + be / be -ing / have + pp · 50%: might / may / could + ... · 100% NO: can't / couldn't + ... · Past = modal + have + past participle
must have /ˈmʌstəv/ · might have /ˈmaɪtəv/ · can't have /ˈkɑːntəv/

CEFR B2 · 60 minutes · Teenagers and adults

Procedure: Modals of Deduction, step by step

Warm-up5 minutes · Pairs, then whole class

Aim: To engage students in speculating.

Show (or describe) three close-up photos of everyday objects (the bristles of a toothbrush, the inside of a mango, a coconut shell).

Pairs guess: "It might be ... It can't be ..." (2 minutes). Reveal the answers.

Presentation20 minutes · Individual, pairs, whole class

Aim: To present modals of deduction in context and clarify certainty, form and pronunciation.

Part A: Reading (6 minutes)

Give out Handout 1. Say: "Read about Tharushi. Where do you think she is? Three minutes."

ICQs: "Who is missing?" (Tharushi.)

Pairs share their theories in any language they have.

Part B: Noticing (4 minutes)

Say: "Read the friends' comments at the bottom. How sure is each speaker? Write 100%, 50% or 0% next to each." Pairs compare.

Part C: Clarification (10 minutes)

Build the certainty scale on the board using the friends' comments.

Ask the CCQs. Point out can't (not mustn't) for negative certainty.

Form. Show present (must be), continuous (might be studying) and past (must have gone). Elicit the past participle in each past example.

Pronunciation. Drill weak have: She must have gone to the library. He can't have seen her.

Controlled practice10 minutes · Individual, then pairs, then whole class

Aim: To practise the forms accurately.

Give out Handout 2. Say: "Exercise A: complete with must, might or can't in the correct form. Exercise B: correct the mistakes. Seven minutes."

Pairs check and explain their certainty. Check as a class.

Freer practice18 minutes · Groups of four, then whole class

Aim: To use deductions fluently and logically in a group mystery.

Say: "New information about Tharushi arrives. Each time you get a clue card, discuss and update your theory. Use must, might and can't, and always give a reason."

ICQs: "What must you always give?" (A reason / the evidence.)

Give each group clue card 1 (Handout 3). After 2 minutes, give clue 2, and so on, until all five clues are out (10 minutes).

Groups write their final theory in three sentences and present it (6 minutes).

Reveal the solution (on the last clue card, which you keep). Groups get a point for each correct deduction (2 minutes).

Feedback and wrap-up7 minutes · Whole class

Aim: To give feedback and consolidate.

Board sentences heard during the mystery: correct and incorrect. Students correct the errors.

Ask: "How do you say you're sure something didn't happen?" (can't have + pp.)

Set the homework.

Homework Find a strange or mysterious photo online or in a newspaper. Write 150 words explaining what might have happened, using at least six modals of deduction.

PPP (presentation, practice, production). Stage times add up to 60 minutes.

Differentiation

Support
Keep the certainty scale on the board and give a sentence-frame card: She must / might / can't have ... because ... Give weaker groups the clues with key words highlighted.
Stretch
Stronger students add could have and couldn't have, and may well have. They challenge other groups' theories: But if she had gone to the library, her friend would have seen her.

Adapting the lesson

ForWhat to change
A large class (40 or more)Keep the pairwork in "Freer practice" in fixed pairs rather than a mingle, and take feedback from four or five pairs instead of the whole room. Monitor one half of the room during "Controlled practice" and the other half during "Freer practice".
A class with no photocopierPut the exercises from Handout 2: Certainty Scale and Practice on the board for learners to copy into their notebooks, and read any text aloud twice instead of printing it. Handout 3: Clue Cards (cut up; give one at a time) works read out from the front: learners note what they need rather than holding a card. The board plan above is this lesson's minimum - with that on the board, it runs on no paper at all.
An online classSend Handouts 1 to 3 in the chat before the lesson and put the board plan on a shared slide. Use breakout rooms for the pairwork in "Freer practice" and visit each room once. Have learners type the controlled answers in the chat, so you see every answer at once instead of nominating.
A different age groupWith teenagers, shorten the analysis and get to the task sooner. With adults in a work context, keep the forms exactly as they are and swap the lesson's theme for one from their own field.

Checking learning

Students use can't (not mustn't) for negative deduction. Past deductions use have + past participle correctly. 8 out of 10 or better on Handout 2, Exercise A.

Teacher's reflection

Did students give evidence for their deductions? Were past forms accurate?

Handout 1: The Missing Student

Name: ______________________________ Date: ______________

It's 4.30 pm. Tharushi, 16, didn't come home after school. Her mother is worried. Here's what we know:

What her friends say:

Kasun: "She must be with Nimesha. They're always together." Dilan: "She might be at the pool. She took her swimming bag." Ishara: "She can't be at home. Her mother would know!" Ravi: "Her phone must have run out of battery. She always forgets to charge it." Amaya: "She can't have forgotten about her mother. She's very responsible."

How sure is each speaker? Write 100%, 50% or 0%.

  • Tharushi left school at 1.30 pm.
  • Her phone is switched off.
  • She took her swimming bag this morning, but it's Tuesday and she usually swims on Thursdays.
  • Her best friend, Nimesha, is also not answering her phone.
  • There is a big school swimming competition next Saturday.
SpeakerHow sure?
Kasun
Dilan
Ishara
Ravi
Amaya

Handout 2: Certainty Scale and Practice

Name: ______________________________ Date: ______________

A. Complete with must, might or can't and the correct form of the verb.

B. Correct the mistakes.

  • The lights are off. They ______________________ (be) out.
  • He didn't say hello. He ______________________ (see) us.
  • I'm not sure where she is. She ______________________ (be) in the library.
  • The ground is wet. It ______________________ (rain) last night.
  • She ______________________ (forget) the meeting. I reminded her this morning.
  • Don't call him now. He ______________________ (sleep). He works nights.
  • That ______________________ (be) Ravi's bag. His is red, and this one is blue.
  • They ______________________ (take) the bus. It's possible, but they usually walk.
  • You ______________________ (be) hungry. You haven't eaten all day!
  • He ______________________ (lose) his keys. He's looking everywhere.
  • He mustn't be at home. The car isn't there. ______________________________
  • She must have went home. ______________________________
  • They might left early. ______________________________
  • It can't be rain. The sky is blue. ______________________________
100% YES50%100% NO
must + be / be -ing / have + pp
might / may / could + be / be -ing / have + pp
can't / couldn't + be / be -ing / have + pp

Handout 3: Clue Cards (cut up; give one at a time)

Our final theory:

..........................................................................................

..........................................................................................

..........................................................................................

Clue 1 (4.45 pm): Nimesha's mother says Nimesha is at home, sick in bed, and hasn't seen Tharushi today.
Clue 2 (5.00 pm): The swimming pool receptionist says a girl in a school uniform came in at 2.30 pm with a swimming coach.
Clue 3 (5.15 pm): Tharushi's swimming coach posted on social media at 3 pm: "Extra training today for the team. Big competition on Saturday!"
Clue 4 (5.30 pm): A charger is found on Tharushi's desk at home.
Clue 5 (5.45 pm): Tharushi's younger brother says she told him at breakfast, "I'll be late today," but he forgot to tell their mother.
Solution (teacher only): Tharushi went to extra swimming training for Saturday's competition. She told her brother, but he forgot to pass on the message. Her phone ran out of battery because she left her charger at home.

Answer Key

Handout 1

Kasun 100% (must) · Dilan 50% (might) · Ishara 0% (can't) · Ravi 100% (must have) · Amaya 0% (can't have)

Handout 2, Exercise A

Handout 2, Exercise B

Common errors to watch for

  • must be · 2. can't have seen · 3. might be · 4. must have rained · 5. can't have forgotten · 6. might be sleeping / must be sleeping · 7. can't be · 8. might have taken · 9. must be · 10. must have lost
  • He can't be at home. · 2. She must have gone home. · 3. They might have left early. · 4. It can't be raining.
ErrorCorrection
He mustn't be at home. (deduction)He can't be at home.
She must have went home.She must have gone home.
They might left early.They might have left early.
He must of forgotten.He must have forgotten.

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About this lesson plan

Written by RCF English to the RCF English international standard: levelled by the CEFR, original throughout, and suitable for classrooms in any country. Last reviewed 22 September 2026.

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