A 32-year-old Lyndhurst woman, a second-grade teacher, has been arrested and charged with aggravated sexual assault and endangering the welfare of a 15-year-old girl from the Jersey City school where the woman is employed, authorities said Friday.Bergen County John L. Molinelli said Lauren H. Mitchell was arrested after an investigation by his office’s Special Victims Unit and the Lyndhurst Police Department.Molinelli said several teachers at the Dr. Lena Edwards Academic Charter School in Jersey City observed what they believed was inappropriate behavior between Mitchell and the girl during a class trip and reported what they had seen to school...