(Undated) -- Many schools in Iowa and around the country are taking precautions over a new TikTok challenge. The challenge reportedly calls on students to commit acts of violence on school grounds on December 17 and calls it American School Shooting Day. Some schools have sent letters to parents urging them to talk to kids about school safety. Police departments across the U.S. say while the threats don't appear to be credible, they're urging parents to notify them if their children hear of anything specific. TikTok says it hasn't found any evidence of such threats originating on the platform.