ST. CLOUD - Cathedral High School students were given a simple but effective question to guide their social media posting on Tuesday.

"Would your Grandma approve if this went up online or if you sent that message?"

Dave Eisenmann speaks to Cathedral students. (Dan DeBaun, WJON)

Speaker Dave Eisenmann, the director of instructional technology and media services at Minnetonka public schools, engaged students in his presentation on "being a good digital citizen." He discussed four key areas: cyberbullying, avoiding inappropriate material, privacy online and digital footprints.

During the presentation, students were allowed to interact with live-texting polls. Cathedral students revealed their most used smart phone app by far was Snapchat, a photo/video messaging app that allows you to send 'snaps' to their friends. Users set a time limit at 10 seconds or less for how long their friend can view the snap before it disappears from their phone.

"It's really good when you don't see people a lot, because you're able to see their face and it's more realistic I guess," Cathedral student Tabetha Durdall says.

"You can take funny videos, it's really just fast and easy," Cathedral student Erika Barthelemy adds.

Eisenmann says the rise of Snapchat gives students another way to keep in touch, but it's also leading to more cyberbullying and inappropriate content.

"Snapchat has really exploded in the past year or so. When I give talks across Minnesota, it's one of the most popular tools being used by 6-12 graders across the state," Eisenmann says, "It gets troublesome when inappropriate content is sent, the other user can always take a screenshot."

Snaps are only supposed to last for a few seconds, but Eisenmann told students that each one never goes away completely.

"Parents and kids need to realize that with Snapchat, the content that they're sharing and that they think only lasts for 10 or less seconds, can actually last a much longer time. Storage is becoming so cheap that it's really nothing for companies to gather your personal data and photos."

After the presentation, students say the "Grandma Rule" stood out to them as an easy way to guide their social media posting.

"I have a lot of social media like Facebook and both of my Grandma's are on there. They can see all of my photos so that stood out to me. I'm always working to be careful on social media," Cathedral student Alexandra Leintz says.