Keeping nude selfies on your phone is a bad idea.

Teacher Leigh Anne Arthur speaks to a reporter in Union County, S.C. Some South Carolina high school students are calling for the return of Arthur who resigned after a student spread a nude picture of her through text messages and social media. (WYFF News-4 via AP)

Credit: George Mathis

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Credit: George Mathis

It's a career-ending bad decision if you happen to be a high school technology teacher who doesn't set up a password and leaves a smartphone with students.

South Carolina teacher Leigh Anne Arthur, 33, left her phone in a classroom and a 16-year-old male student used his phone to take pictures of the "Valentine's Day" photos Arthur intended for her husband's eyes only.

The student digitally distributed the photos to every Union County classmate who wanted a copy.

The teen didn't try to hide his actions. According to Arthur, he told her her "day of reckoning" was coming soon.

That day arrived swiftly. Arthur was asked to resign from teaching because her unlocked phone was thought to have contributed to the delinquency of a minor.

"This is a case where a staff member, properly supervising students, could have prevented a very serious problem," the school system said in a press release.

The student, who is now in juvenile detention, sounds like he may have gone astray before looking at his teacher's phone. Four of the racy photos were printed out and placed in her home mailbox along with a "threatening" note. Arthur's husband checked the mail that day and found the Valentine's Day gift that keeps on giving. The note is being checked for fingerprints.

Police have charged the boy with "aggravated voyeurism" for taking and distributing the photos without permission. The teen's phone was inspected and found to contain a hidden folder containing his teacher's photos. Shockingly, police also found other nude pics on the 16-year-old male's phone.

Arthur, who does not teach English, departed with one final lesson for her likely least-favorite student.

"I forgive you. It don't make it anymore right. But what's done is done and I hope you learned your lesson. And I hope that you learned from this mistake and I hope that you have a wife one day that you treat like gold and you won't want this to ever happen to her," she said in February.

That's nice, but it's not as helpful as a tricky password.