A convicted sex offender is behind bars after entering a grade school on Wednesday. 23-year old Nicole M. Hobbs of the 100 block of Ohio Avenue has been charged with aggravated battery, threatening a public official, presence within a school zone of a child sex offender and criminal damage to government property. Police say Hobbs entered South Roxana Grade School during a lunch program, prompting an anonymous tip from the public. After being taken into custody at her home Hobbs allegedly became combative, kicking an officer, damaging dry wall in the South Roxana Police Department booking room, kicking the Police Chief and threatening to kill him and his family after her release. She is being held at the Madison County Jail on a $100,000 bond.