(CNN) Emily Lavelle and her friends were bored after school one day and decided to call the suicide prevention hotline, listed on the back of their middle school student ID cards.

What they discovered on the other end of the line was something very different.

Emily had unintentionally called a sex hotline. The phone number was listed as a resource on the student ID cards issued by New Vista Middle School in Lancaster, California.

Emily told her mother, Janene, about the discovery Monday after being picked up from an after-school program.

"First thing I did was call the number, and sure enough, it was a sex line," Lavelle told CNN. "I was pretty shocked -- it was kind of disbelief."

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