(Sioux City, IA) — Nine students have been charged in Woodbury County with making threats on social media that were aimed at their schools. Local officials are asking parents to do a better job of monitoring their children’s social media use. Woodbury County Attorney P-J Jennings says it’s possible the parents will be held accountable depending on the results of an investigation. Jennings says parents have to convince their kids the threats aren’t jokes and won’t be taken as jokes. They were disruptive. An estimated 20 percent of district students didn’t attend class Friday.