@abcnews: An investigation is underway at a Texas elementary school after preschool teachers allegedly distributed stickers to students that are believed to be sleeping aids. Lisa Luviano, the mom of a 4-year-old student at Northgate Crossing Elementary School in Springs, told ABC News station KTRK-TV that her daughter came home from school with a sticker featuring a starry-night like design. Luviano said she believes the sticker placed on her daughter was melatonin, a hormone that plays a role in sleep, according to the National Institutes of Health. The day after the conversation with her daughter, Luviano said she went to the school to report the sticker. She told KTRK she believes her concerns were not immediately addressed.