Many of them knew him as Mr. Walz, the fun geography teacher, but the students lucky enough to sign up for a classroom seat in seventh and eighth period Thursday got to know Congressman Walz.

About how he votes using a special I.D. card embedded with a chip — and how he once tried to use his ATM card in its place. About how he deals with his attention deficit hyperactivity disorder and whether many members of Congress have ADHD (“a lot,” he guesses). And about how he was once pulled aside by airport security, taken to a small room and put to a random search.

For the first time since beginning unpaid leave a year ago this week, Rep. Tim Walz was back at West High School, where he taught global geography since 1996.

But his lecture seemed less like a homecoming than a quiet visit.

The name of his press secretary, Meredith Walz, is still printed above the chalkboard as recognition for a perfect score in a college-level test.

Scott Urban, a fellow teacher who hosted the visit, called Walz a “regular guy.”

And Jenny Buesing, a senior, had Walz as a teacher last year but worked on his campaign during the summer and fall. She admitted it was a bit “weird” to see her former teacher — the funny guy who was big on discussion, not homework — as a United States Representative.

He divided his time between a lecture on foreign policy — where he argued that the political ascension of China will make more of a lasting impact on these students than the terrorist attacks of September 11, 2001 — and a Q & A session.

A girl asking about random searches at the airport got an interesting response.

Walz shared some annoyance about being taken aside and searched. Not so much because smooth air travel ought to be his special privilege, but just because of the likelihood of a Congressman being a terrorist.

Nathaniel Wolf asked Walz how many members of Congress had ADHD.

Walz is a fast talker who said he had ADHD, before his wife and assessment coordinator for Mankato Public Schools Gwen Walz gently reminded him that it was “undiagnosed” ADHD.

“No, I’m not diagnosed, but it’s pretty obvious,” he joked.

He also showed the class the special keycard he inserts in a machine to vote. Once, just minutes before time ran out to vote, he panicked after it didn’t work. This, until a polite page informed him that he was trying to use his ATM card.

But his most important message was about participation in government.