AUSTIN, Texas — Kids are back in class, which means they're catching up with friends they haven't seen all summer. So, it won't come as a surprise when you see your teens glued to their phones again.

Police said now is the time to have an important conversation with your kids. Things can get a little hectic at the start of the school year, but officers said you shouldn't neglect what you're kids are doing online.

It's not new – sexual predators use social media to get the attention of teenagers.

In fact, research shows that 40% of fourth- through eighth-graders have connected with a stranger online.

RELATED: Social media, television use could be a depression risk for teens, study finds

Police around the country want parents to be on the lookout for potentially dangerous apps that your kids might have access too.

Not all the potentially dangerous apps will stick out. One app is even disguised as a calculator. That one can hide photos, videos and your chid's browser history.

In July, a sheriff in Oklahoma shared a graphic with 15 apps parents should be aware of.

RELATED: Here are 15 apps parents should look out for on their kids' phones

Some of them you might recognize such as "Tiktok" and "WhatsApp," but there are other location-based dating apps police said you need to pay attention to. Those apps include "MeetMe," "Grindr" and "Skout."

Don't look past the popular ones like Snapchat or Instagram, because cops said kids can be targeted there too.

It's not just apps parents should be concerned about. You should also talk to your kids about suggestive or revealing selfies.

Police said once a certain picture or video leaves their phone and is sent to someone else, it is out of your control.

WATCH: Screenwise App helps parents get their kids off devices

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