The School Rules Mystery – Learn “Must vs Have To” Grammar Story

Rose Sensei
Oct 8
3 min read

Updated: Oct 29

Do you know when to use must and when to use have to?

These two modal verbs both express obligation — but they’re not always the same!

In this post, you’ll learn the difference through a fun short story, The School Rules Mystery. It’s perfect for Pre-Intermediate and Intermediate ESL learners who want to learn English grammar in a natural, story-based way.

Two cartoon characters in a classroom discuss "MUST x HAVE TO" on a board. A third character observes. Title: "The School Rules Mystery."

Watch:

🎥 SHORTS video: Must vs Have To - What's the difference?

🕵️‍♀️ Story: The School Rules Mystery

It was Monday morning at Maplewood High School. The students were whispering nervously in the hallway.

Something strange had happened overnight — the school rules poster had disappeared!

Miss Carter, the head teacher, looked serious.

“Everyone must follow the rules,” she said. “But first, we have to find out who took the poster!”

Emma and her best friend Leo decided to investigate.“We mustn’t tell anyone yet,” Emma whispered. “The person who took it might still be around.”

They checked the library. “You have to be quiet in here,” Leo reminded her.

They looked behind bookshelves, under tables, and even in the art room.

Then they saw something unusual — a piece of paper stuck to the noticeboard.

It read: “If you want to know the truth, check the lost and found box.”

Inside the box was the missing rules poster!

On the back, someone had written:

“New rule: You must smile every morning!”

Everyone laughed. Miss Carter smiled too.

“Well,” she said, “that’s a rule I think we have to keep!”

🧠 Grammar Focus: Must vs Have To

Expression	Meaning	Example
Must	Personal obligation (from the speaker)	You must finish your homework tonight.
Have to	External obligation (rule or law)	You have to wear a seatbelt.
Mustn’t	Prohibition	You mustn’t run in the hallways.
Don’t have to	No necessity	You don’t have to bring lunch today.

✅ Quick Tip:

✔️You must do something when you feel it’s necessary.

✔️You have to do something when someone else decides it’s necessary (a rule, law, or school policy).

💬 Comprehension Check

Answer these questions after reading:

What disappeared from the school?
Who tried to solve the mystery?
Where did they find the missing poster?
What was the “new rule”?
How did Miss Carter react?

📝 Grammar Practice: Must or Have To?

Choose the correct answer:

You ___ (must / have to) arrive on time for class.
Students ___ (mustn’t / don’t have to) use their phones in lessons.
We ___ (have to / must) wear uniforms at this school.
You ___ (must / have to) listen carefully during meetings.
I ___ (must / don’t have to) stay late today — there’s no homework!

(Answer key available in the downloadable worksheet below!)

☕ Let’s Talk! (Speaking or Writing Practice)

What school rules did you have to follow?
What rules do you think students must follow today?
Do you agree with the rule: “You must smile every morning”?
Why or why not?
What’s one rule you wish you didn’t have to follow?

📚 Why Learn Grammar Through Stories?

Stories make grammar easier to remember!

Instead of memorising rules, you learn in context — just like native speakers do. When you see must and have to used naturally in a story, it’s easier to understand their real-life difference.