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KATY, Texas - Administrators at a Texas high school are alerting parents to a phone app they call "sickening," and have banned it.

The app "Gaggle" allows users to post disturbing messages. One in particular talks about a teacher's "disgusting body" and "horrible personality." Another mentions nude photos and sex acts being performed for $20.

The message appear to have been posted by students at Seven Lakes High School in Katy, and now the principal is putting a call out to parents, asking them to have the app deleted from their child's phone.

In an email home, the principal said he is sickened and saddened by what he's seen.

Debbie Libby got that email from Principal Ted Vierling and says she is going to talk to her kids about Gaggle.

"They show each other Instagram pictures and Facebook a little bit, but I've never heard of this one," said Libby.

Other parents tell KPRC-TV they've gone on the app themselves and what they've seen isn't good.

That's why Seven Lakes is now blocking Gaggle from the public WiFi and asking parents to monitor things at home.

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