Primary English | Modal Verbs for Tutors | Four modals, a certainty scale, no to after

2026-11-04

Tutor lesson-prep guides · Primary English

Pupils write He musts go and He should to go because they treat a modal like an ordinary verb. This lesson fixes it with two hard rules and one certainty scale.

Objectives — Pupils can: (1) explain what each of the 4 modals does: must for duty, should for advice, can for ability, might for possibility; (2) keep the base verb after a modal and never add s, even with he or she; (3) rank might, should and must on a 0 to 100 percent scale and say why.

01 Prerequisites (3-minute check)

If any of these fails, fix it before the lesson starts.

Skill	Quick check	Pass mark
Base verb	Give the base form and the third person of go	go and goes
Negatives	How is a present simple negative formed?	do or does plus not
Degree words	How do possible and certain differ?	Possible may not happen, certain must

02 Lesson flow (60 minutes)

Time	Stage	Tutor does	Student does
0-8 min	Two sentences	You must wear a helmet beside You should wear a helmet	Say how the tone differs
8-18 min	Four modals	Two sentences each for must, should, can and might	Groups of four fill a table
18-34 min	Two hard rules	Base verb after a modal, and no s on the modal	Rewrite eight sentences
34-46 min	Certainty scale	might 50, should 70, must 100 percent	Rank them once
46-56 min	Negatives and past	must not against do not have to; past duty uses had to	Correct alone
56-60 min	Exit check	Three questions collected and marked	Work alone

03 Teaching script (read it out)

Scene 1: Ask whose rule it is before ranking the tone

must carries the speaker authority (You must finish it today), should gives advice (You should sleep earlier), can marks ability or permission, and might marks an uncertain possibility.
Use one situation four times: a mother saying must, a teacher saying should, a classmate saying can, a forecast saying might. Pupils hear at once that the four words are not synonyms.

Pupils do: place four sentences into rule, advice, ability and possibility, with a reason.

Scene 2: Put the two hard rules on the board

First, a modal takes the base verb, so any to is wrong (He should to go). Second, the modal itself never takes s, so He musts is wrong. In this lesson the base verb is preceded by to 0 times.
The line pupils repeat: the modal never changes, the verb after it stays bare.

Pupils say: what is wrong with She cans swim.

Scene 3: Turn tone into numbers

Place might at 50, should at 70 and must at 100 percent, keeping can off the scale because it marks ability rather than likelihood. With numbers, must not (0 percent permitted) separates cleanly from do not have to, which means not necessary but allowed.
Close with past duty: must has no past form, so yesterday uses had to.

Pupils do: rewrite one past rule with had to and explain why musted does not exist.

04 Question types and worked steps

Type	Example	Steps	Answer
Gap fill	You ___ wear a seat belt. It is the law.	A legal duty takes must	must
Multiple choice	It ___ rain later, but I am not sure.	Uncertain possibility takes might	might
Correction	He should to see a doctor.	Delete to	He should see a doctor
Rewrite	I must study yesterday	Past duty takes had to	I had to study yesterday

Sanity check (teach this): Checks: 4 modals are taught; the base verb follows to 0 times; the certainty scale runs might 50, should 70, must 100 percent; must not and do not have to are opposites; must has no past form and becomes had to.

05 Independent practice (3 questions)

Question	Answer	What to watch
Four-column sort	8 sentences into rule, advice, ability and possibility	must and should must not be merged
Eight corrections	One error per sentence: to, s or tense	Name the rule behind each fix
Certainty ranking	Order four sentences from most to least certain	can stays out of the ranking

06 Common mistakes and what to say

Mistake	Student writes	Say this
to after a modal	You must to finish it.	A modal takes the bare verb, so no to ever appears between them.
s on a modal	She cans swim very well.	The modal never changes; can stays can with she.
must not for not necessary	You must not come if you are busy, meaning you need not come.	must not forbids; not being necessary is do not have to.
ed on must	I musted go to the clinic.	must has no past form; past duty is had to.

07 Homework (paper, section and question numbers)

Primary 5 English paper: grammar — Section B: pick three modal items
Primary English chapter index — Compare with the other chapters
Redo this chapter — Write one sentence per modal and read them aloud

08 Exit check (last 5 minutes)

Question	Answer	Decision
What follows a modal?	The base verb, never to	Answering to means replay scene two
What does must not mean?	It forbids	Answering not necessary means replay scene three
Past form of must?	had to	Answering musted means replay scene three

09 Tutor FAQ

How does must differ from have to?

must comes from the speaker, have to comes from an outside rule. At primary level they often interchange, but must not and do not have to must stay apart.

Why teach percentages for possibility?

Words like possible are too vague to rank. Numbers make the strength of might against must visible.

Why keep can off the scale?

can marks ability or permission rather than likelihood, so putting it on the same scale creates confusion.

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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.