It's been four years since a fifth-grade maths teacher's simple-yet-brilliant idea to prevent bullying garnered national attention, but it's still making waves online.

Back in 2014, author Glennon Doyle wrote about how her son's teacher [1], Cathy Pitt, used a simple piece of paper once a week to gather clues as to which children in her class were being left out, feeling lonely, or possibly even at risk of being bullied.

"I simply hand out an index card to each child," Cathy, who teaches at Sea Gate Elementary School in Florida, told the Today show [2]. Then, she tells the kids, "On the back of your cards, make sure you list someone that you know you want to get to know."

Thus, by form of secret ballot, she has her students highlight an exceptional classmate along with a few names of fellow students they'd like to work with on the next group project.

"When I came up with the idea of simply distributing the cards, it really was to find out which children were belonging and which children were not," she said. Every single Friday, after the students went home, she'd review the cards and look for patterns:

Who is not getting requested by anyone else?
Who doesn't even know who to request?
Who never gets noticed enough to be nominated?
Who had a million friends last week and none this week?

Although the cards made it clear to see the most "exceptional" students, it was the names that showed up the least that Cathy needed to monitor the most, and she would.

Doyle, whose blog post on Pitt's trick was shared more than 4 million times in the first week it was published, said that Cathy had been doing this for the past 20 years – since the school shooting at Columbine. "That was the day she realised that kids have to be seen," Doyle said. "And they can fall through the cracks."