A teacher in the US state of Idaho is horrifying the internet with the "disgusting" - and effective - way she taught her students about the importance of classroom cleanliness.
Jaralee Metcalf, a behaviour specialist, worked with special education teacher Dayna Robertson to put on an experiment that would teach their elementary school students "why we're constantly telling them to wash their hands," BuzzFeed reports.
The lesson, which they adapted from a post on the C.S. Mott Children's Hospital's website, involved tracking the growth of mould on five different pieces of bread - which were kept in plastic sandwich bags and hung on a classroom wall.
One piece of bread was placed in its bag untouched, but the other four were exposed to other things commonly found in a school building. The first "contaminated" piece of bread was rubbed on one of the classroom's Chromebook computers; the second was touched by a child with unwashed hands; the third was touched by a child who washed their hands with hand sanitiser; the last one was touched by a student who washed their hands with soap and water.
The bags were left hanging for just a few days before varying degrees of mould started to form on each piece of bread, in a result that Metcalf called "disgusting" after sharing the experiment on Facebook.
"As somebody who is sick and tired of being sick and tired of being sick and tired. Wash your hands!" Metcalf wrote. "Remind your kids to wash their hands! And hand sanitiser is not an alternative to washing hands!! At all!"
Metcalf's post has been shared more than 60,000 since she first shared it earlier this month, with thousands of commenters weighing in to applaud the lesson's importance. Still, the educator advised others to avoid judging the children themselves.
The behavior specialist said the experiment was personally important to her as well, as dirty classrooms have often led to her husband, her infant child and herself getting sick at home.
And the results of the lesson certainly send a message. Each of the bread slices - except for the untouched piece and the one touched by a child with soap-and-water-washed hands - contained a more-than-noticeable amount of mold. The slice wiped on the classroom's Chromebook was almost entirely green and black.
Metcalf said the students definitely took the lesson to heart, telling BuzzFeed that she hopes the experiment will make everyone's lives healthier - hers included.
"Nothing is more frustrating than working with an obviously-sick kid all day long and then potentially bringing that illness home with me," she said. "Hand washing can only go so far."