A. Pawlowski, TODAY contributor
Melissa Bour teaches sixth grade science and math, but it’s her lesson on social media that’s really striking a chord with children and their parents.

Alarmed by some of the images she saw on Facebook, Bour — who works at Emerson Elementary School in Tulsa, Oklahoma — wanted to show her students how quickly photos and comments they post online can spread.

Video: A sixth-grade teacher has received responses from around the world after posting a letter to Facebook about her students’ inappropriate social media sharing. The post was shared in 33 states and four other countries within eight hours, spurring some of her students to delete Facebook posts or even their entire pages.

“I noticed more and more pictures were showing up that were inappropriate,” she told TODAY. “So I used a teachable moment. I got out a piece of computer paper and a green pen and I wrote a little note.”

The letter, which she wrote in all caps and simply addressed to “Dear Facebook,” read in part:

“My 12-year-old students think it is ‘no big deal’ that they are posting pictures of themselves in bras or with their middle finger in the air. Please help me out by sharing this image and commenting with where you live to show these young students how quickly their images can get around.”

Within hours of posting it on her Facebook page earlier this month, Bour’s letter went viral. It has since reached all 50 states plus dozens of countries around the world, including Australia, Saudi Arabia, England and Germany.

Bour has deleted the original post, but copies of it continue to circulate — another important lesson for her students. Just because you delete a social media post or a photo, doesn’t mean it’s completely erased from the Internet.

Bour’s students say the experiment showed them that what they do online now could haunt them in the years to come.

“I’m not going to put any more photos on my Facebook and I’m not going to comment on anything that I like or dislike,” said Peyton Piguet.

“Say I want to be the president. That might affect me becoming president,” added Xavier Ingram.

Parents are praising Bour’s approach, too.

“We don’t elaborate enough as parents telling our kids ‘no all the time. What Miss Bour did, it gave them more of an understanding of why we’re saying no to our children,” noted Kalecia Thomas.

Meanwhile, Bour has also learned a lesson from the experiment: She’s now more aware of what she posts online so that she can set a good example for her students, she said.