The Grade 8s were too intimidated to enter the school's graffiti-riddled C-wing, and the cafeteria was a teenage jungle where the weak were trampled and the biggest kids ate first. That, however, was before David Derpak took over as principal of Killarney Secondary School.

In 2009 – a particularly bad year – the hardscrabble school on Vancouver's east side had experienced a rash of vandalism, suffering more than $8,300 in broken windows alone. False fire alarms, locker break-ins and drug deals were so common that teachers requested surveillance cameras be installed throughout the hallways.

That changed soon after Mr. Derpak – a 52-year-old, 200-pound Mr. Clean lookalike, minus the earring – arrived in the summer of 2010. In less than two years, his unconventional, sometimes controversial methods have helped turn around the school of some 2,100 students. Suspensions and absenteeism are down 30 per cent, late arrivals are down 39 per cent, the graffiti is gone and the near-weekly prank fire alarms have all but stopped. The infamous C-wing is now a crisply painted thoroughfare where candidates for student government hang campaign posters.

Story continues below advertisement

The C-wing was ground zero for Mr. Derpak's key turnaround strategy, a hallway monitoring technique he calls "platooning." Mr. Derpak – a Vancouver native and former gym teacher whose family tree is filled with educators – and his two vice-principals would constantly rove the hallways, staying in touch over walkie-talkies and developing code names for different parts of the school. Every school day they mapped out a new plan of attack designed to keep students guessing.

"The students have to feel like you're always watching," Mr. Derpak said in a recent interview in his office, his files neatly arranged next to his computer in ascending order of priority. "If you bring order to a place of chaos, my theory is, the rest will follow."

While academic gains at Killarney have been modest – the school's Fraser Institute ranking remains constant – consensus among teachers, parents, students and even the graffiti artists is that Killarney is a far better place than it was three years ago.

Still, Mr. Derpak's tough-love approach flies in the face of educational orthodoxy, leading to comparisons, not always favourable, with former New York mayor Rudy Giuliani and his so-called broken-windows strategy – cracking down on minor offences such as graffiti, vandalism, public intoxication and panhandling to forestall bigger crimes.

Story continues below advertisement

While many credit "broken windows" with cleaning up New York in the 1990s, crackdowns aren't the way to turn a school around, according to Jeff Kugler, a former principal in Toronto's downtown Regent Park neighbourhood and executive director of the Centre for Urban Schooling at the University of Toronto.

"Maybe in the short run it could work, but in the long run you don't change people's attitudes, beliefs and connections to places by increasing and enforcing rules," he said. "I think in the end that becomes just another thing to get away with."

In the early days, students at Killarney – even the council president types – were definitely skeptical of their new principal and his team of bellowing vice-principals. "Those walkie-talkies were popping up everywhere, like magic elves," recalled 17-year-old Manraj Randhawa.

The smoke-bomb incident changed everything. Six weeks into Mr. Derpak's tenure, two senior boys decided to set off a homemade smoke bomb in a garbage can in the crowded cafeteria. Orange flames burst three feet into the air and a thick plume of smoke poured out, sending students running for the exits.

Story continues below advertisement

Mr. Derpak knew the students were watching, waiting for his next move. Within an hour he addressed the entire school over the PA system. He described how firefighters were forced to leave more important calls to come attend the school and how the blast had left a teacher's Seeing Eye dog – a golden Labrador retriever named Tempo – shaking with fear. "You have to play on the kids' emotions," Mr. Derpak said.

Then, the principal dropped his own bomb: He offered a $500 reward to any student who would name names.

In the minutes after that announcement, you could hear a pin drop in the hallways at Killarney. The way the kids told it, most were doing the mental math of how much $500 could buy, while others just got nervous.

"It was like Crime Stoppers," recalled 16-year-old Solomon Dikran, who was in Grade 10 at the time. "I'm not going to lie – some of my friends were, like, 'This guy is crazy.' "

Story continues below advertisement

But within 24 hours, two students had come forward. They shared the reward – which came largely from the school's vending machine (though Killarney lore is the money came from Mr. Derpak's wallet) – and two students were expelled. (One of them won an appeal.)

"After that smoke bomb, everything was different," Solomon said. "No one was going to do anything wrong."

It wasn't just the students who changed. After the smoke cleared, a softer side of Mr. Derpak emerged. He bought sweatshirts for the girls' hockey team and made students laugh complaining about the texture of the chia-seed smoothies that his wife, who teaches elsewhere, serves him every morning. His platooning technique had the benefit of helping him learn students' names and provided an opportunity for him to share the photos he keeps on his iPhone of his three pet chihuahuas – one a rescued animal named Gracie-Anna. Having repaired the broken windows, he started to build bridges.

Mr. Derpak learned the power of bonding with students 30 years ago, during his teaching practicum in Maple Ridge, B.C. It was there that he taught a visually impaired Grade 10 student – who had previously always sat out during gym class – how to play football. The class rallied around the student and eventually helped him score a touchdown.

Mr. Derpak's hands-on approach has caught the attention of local educators, including Vancouver School Board chair Patti Bacchus.

Story continues below advertisement

"He knows those kids. He knows their stories. He knows what they're doing this weekend," she said. "It just changes the tone of the school."

For Solomon Dikran, now in Grade 11, that change was most evident early this school year, when he bumped into one of Killarney's vice-principals in the hallway on his way to class and realized he wanted to talk to him.

"Usually you only talk to a principal because you're in trouble," he said. "But I suddenly realized that talking to a principal wasn't weird anymore. That's huge."