A special education teacher in the New Haven, Connecticut public schools has been charged with sexually assaulting three underage students, according to police. Robert Schmitt, of Hamden, turned himself in to police on Wednesday, police spokesman David Hartman said in a press release Thursday afternoon. Schmitt, 48, is accused of assaulting three students during the 2011-2012 school year at the MicroSociety Magnet School. Each of the alleged assaults took place when the child was under the age of 13, Hartman said. The police investigation of Schmitt began in April, when a school social worker heard an allegation from a student -- a 12-year-old girl -- and reported it, Hartman said. A second victim, a 14-year-old girl, came forward in May, and two days later detectives spoke with the third victim, a 12-year-old boy.