A former student once stopped me and asked a question I wasn’t expecting.

“Do you still take your students on that cryptography field trip?”

I told him I did.

“Good,” he said. “You should do that every year.”

And then he went on with his day.

I didn’t.

I kept thinking about it.

That field trip?

Don’t get me wrong. It was a great field trip.

The summer before that year, I had spent weeks doing research with a professor at the University of Cincinnati. Our work focused on introducing younger students to cryptography, and together we developed a math unit that allowed students to discover some of its history by experiencing the problems that shaped it.

Basically, we turned my classroom into a place full of spies and hackers.

Students had to send secret messages from one room to another through a third party determined to intercept them.

They developed secret keys.

The hackers cracked them.

They developed better systems.

The hackers adapted.

Eventually, the need to keep their messages secret led students into surprisingly sophisticated ideas about cryptography.

Never underestimate the educational power of a sixth grader determined to keep a secret.

The professor visited our classroom to see the project in action and later invited my students to the university.

They met someone from the NSA.

They touched a real Enigma machine.

They played logic games.

They toured the College of Computer Science.

It was fun. It was challenging. It was a wonderful day.

And then we came back to school.

The year continued.

We learned other things. Took other field trips. Had other experiences.

In my mind, that day became one small part of a much larger school year.

A blip.

Apparently, not for him.

Years later, of all the things he could have asked me about, he wanted to make sure other students were still getting that experience.

I wish I had asked him why.

Was it the Enigma machine?

Meeting someone from the NSA?

Walking around a university?

The cryptography?

I don’t know.

And maybe that’s the point.

As teachers, we spend an extraordinary amount of time thinking about what students need to learn.

But I’ve started wondering about something else.

What did they get to experience because they spent this year with me?

That’s a different question.

Because a school year isn’t only a collection of things children learned.

A school year is a collection of experiences children have lived.

They wrestled with a question.

Built something that didn’t work.

Had an idea nobody else had.

Changed their mind.

Touched an Enigma machine.

Laughed.

Discovered something they didn’t know existed.

Maybe even caught a glimpse of a world they might someday want to enter.

And we have some say in what gets put into that collection.

Not every day needs to be extraordinary.

Not every lesson needs to become a memory.

But every once in a while, something we thought was simply one more part of the school year leaves with a child.

We may never know which thing it will be.

Some lessons end when the bell rings. Others leave with the students.

Years later, one of mine came back carrying cryptography.

I’m really glad he told me.

Because now, when I think about the year ahead, I’m not only asking what I want my students to learn.

I’m asking something else too.

What will they get to experience because they spent this year with me?