TROPHY CLUB -- Northwest school district officials received an anonymous tip in December saying a pregnant middle school teacher was having relationship with a student, according to an arrest warrant affidavit.

Katherine Ruth Harper, 27, is accused of having sex multiple times with a 15-year-old male student last summer at her Fort Worth home and his home in Trophy Club, the affidavit stated.

During the times the two met, Harper, a teacher at Tidwell Middle School in Roanoke, and the student exchanged several naked pictures of each other using their cell phones, according to the affidavit obtained by the Star-Telegram late Wednesday.

The teen saved the photos to his phone, police said. The teen is not being identified because he is a juvenile.

A three-month investigation of the allegation ended last week when Harper was arrested and later released from the Denton County Jail after posting $15,000 bond.

She faces a charge of improper relationship between an educator and student, a second-degree felony. Harper, who has been on administrative leave, could not be reached Thursday for comment.

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