Tim Walz may be the next US VP. To those he taught, he’s Mr Walz.

Minnesota Governor Tim Walz could be America’s next vice-president. Nobody is more enthusiastic about it than former students in his small-town, midwest classroom.

At Mankato West High School, years before he joined the political scene, a young Mr Walz taught geography and social studies, supervised the lunchroom and coached the football team.

The Harris campaign has sought to highlight Mr Walz’s career as a teacher, even though he served six terms in Congress before he returned to Minnesota to run for governor, a position he’s held since 2018.

Those who knew him back then told the BBC that his teaching history is a guide to the politician he has become and the vice-president he could be.

It was 1999 and Jacob Reitan – the first openly gay student at Mankato West – was part of an effort to form the first gay-straight alliance at the school. GSAs, student-run organisations focused on supporting LGBTQ youth, emerged across the country through the nineties.

Mr Reitan still remembers the bullying he faced back then, from the homophobic insult spray-painted on his driveway to a smashed-in car window in the school parking lot.

But he told the BBC the Walzes promoted inclusion, kindness and “jointly made the school a place where it was safe to come out”.

And because the new GSA required a faculty advisor, Coach Walz stepped up.

“It really needed to be the football coach, who was the soldier and was straight and was married,” he said in a 2018 interview, explaining why he took the role.

Mr Walz remained a firm supporter of same-sex rights and, in 2011, Mr Reitan stood by the then-congressman’s side as President Barack Obama signed his bill repealing the Don’t Ask, Don’t Tell policy for gay and lesbian Americans serving in the military into law.

“He’s so perfect as an addition to the Harris ticket,” Mr Reitan said.

Introducing him on Tuesday at their first joint campaign event, Ms Harris lavished more praise on Coach Walz than on Governor Walz, his current title.

“Tim Walz was the kind of teacher and mentor that every child in America dreams of having, and that every kid deserves,” she said.

“He’s the kind of person who makes them feel like they belong and then inspires them to dream big, and that’s the kind of vice-president he will be.”

The Trump campaign has assailed Mr Walz as “a dangerously liberal extremist” who, along with Ms Harris, forms a ticket that they say is too far left for most Americans to stomach.

They have scrutinised his record as Minnesota’s governor – from enacting an ambitious left-wing agenda to delaying deployment of the National Guard in response to violent protests following the murder of George Floyd.

The Harris campaign is leaning into a biography they believe can win over the rural and working-class voters she needs to defeat Mr Trump this November.

While Ms Harris grew up and built her career in liberal California, Mr Walz spent his childhood fishing, farming and hunting in rural Nebraska and came to politics later in life. He joined the National Guard at age 17.

For about 17 years, from 1989 to 2006, he worked in public high schools – first for a year in China, then in Nebraska and later in his wife’s native Minnesota.

And former students like Mr Reitan are glowing in their praise for the ex-educator.

For brothers Jake and Josh Jagdfeld, attending Mankato West was akin to “home-schooling with the Walzes”.

Josh Jagdfeld took classes with both Tim and Gwen Walz in the 10th grade, and he remembers worrying politics would change his favourite teacher.

But when they met on Monday night, Mr Walz greeted him with a shout of “Mankato West in the building!” and a big hug.

“He’s warm, engaging, cares about everybody he talks to. That’s exactly the same Tim Walz I knew,” Josh Jagdfeld told the BBC.

Coach Walz, a defensive coordinator for the school’s football team, tapped Jake Jagdfeld as line-backer, putting him “in a position to succeed”.

When Coach Walz joined the team, Mankato West was reeling from a winless 0-27 season. Three years later, it won its first ever state championship.

“Great credit goes to him,” Jake Jagdfeld said. “He helped to create an inspirational environment for us young men to feel confident and work hard.”

In 2004, Noah Hobbs was in Mr Walz’s last geography class before he left teaching.

“He’s a very high-energy person, whether school was just starting or it was the end of the day, and that energy was infectious,” he said.

“The level of care that he gave to all students – not just the kids getting 4.0 [GPAs] – was really impactful for me as a young kid.”

Mr Hobbs believes the US is “looking for someone that is authentic, and Tim embodies that in a way not seen in politics at that level very often”.

Mr Walz’s evolution from teacher to politician has been described as accidental.

In his telling, it stemmed from an incident at then-President George W Bush’s 2004 campaign rally in Mankato.

He and another teacher chaperoned two students to the event but local organisers refused to let them in.

“They knew we were Democrats,” Matt Klaber, one of the students, told the BBC.

“At this time, the Bush campaign was turning away any possible protesters from their rallies and this was no exception.”

When Mr Klaber pulled out his ID, the staffers observed a faded John Kerry sticker on his wallet. The students were sent home.

Mr Walz has described being “struck by how deeply divided our country was becoming”. He went on to volunteer for the Kerry campaign, develop his own local contacts and then launched a bid for Congress in 2006.

“The news reports say part of what Kamala was looking for was chemistry and a governing partner,” said Mr Klaber.

“Then picking Mr Walz was a no-brainer. All the good things people have been saying about him as a person are absolutely true.”

When Mr Walz arrived on Capitol Hill, new members of Congress were learning in orientation sessions about their salary and benefits.

“They were talking about, ‘I know most of you are taking pay cuts,’” he told local Minnesota television station KSTP.

“And I leaned to my aide and said, ‘This is four times what I’ve ever made in my life.’