The Problem With “They Should Know This By Now”

There’s a phrase that appears in schools constantly:

“They should know this by now.”

Sometimes it’s said out loud.Sometimes just thought internally while staring at a class collectively forgetting something you taught three weeks ago.

Either way, it usually comes from frustration.

The issue

We assume learning is linear.

Teach it once. Practice it once or twice. Move on.

But that’s not how memory works.

What students actually do

Students forget things.

Constantly.

Not because they aren’t listening.Not because they don’t care.

Because forgetting is normal.

The dangerous assumption

When we think:“They’ve already done this.”

We often:

• explain less clearly

• rush instructions

• skip modelling

• get irritated more quickly

And students notice that immediately.

The reality

A student can:

• understand something in one lesson

• answer questions correctly

• seem confident

…and still forget it later.

That isn’t failure.

That’s memory.

What works better

Instead of:“You should know this.”

Try:“Let’s bring it back.”

Quick recap.Short retrieval.One modeled example.

No drama required.

Why this matters

The classrooms that feel calm and successful usually aren’t the ones where students remember everything.

They’re the ones where forgetting is expected and planned for.

The shift

Good teaching isn’t:“I taught it once.”

It’s:“I know they’ll need to revisit it.”

The mistake to avoid

Treating forgotten knowledge like bad behaviour.

Most of the time, students aren’t being difficult.

They just genuinely can’t retrieve it yet.

Final thought

Repetition isn’t a sign something failed.

It’s often the thing that makes learning stick.

Slightly blunt summary

If they forgot it…teach it again.