SALEM, Mass. - A 14-year-old accused of killing his high school math teacher pleaded not guilty to murder, aggravated rape, and armed robbery Wednesday.

Philip Chism is charged in the Oct. 22 death of Colleen Ritzer, a popular teacher at Danvers High School. Ritzer's body was found in woods near the school with her throat slit and a note reading, "I hate you all."

Chism had already pleaded not guilty in District Court, but the case was moved to Superior Court after he was indicted last month. His attorney agreed Wednesday to a prosecution request that he remain held without bail. The hearing lasted about 15 minutes.

Ritzer's family and friends filled two rows of the courtroom. Chism's mother, Diana, sobbed quietly when he was taken into court.

The families left without talking to reporters. Ritzer's family released a statement saying they "remain devastated" by her death but are "strengthened by the tremendous outpouring of love and support we have received."

Philip Chism had recently moved to Massachusetts from Clarksville, Tenn. Police have not released a motive for Ritzer's killing. Assistant District Attorney Kate MacDougall said Wednesday that nothing during the investigation has pointed to mental-health issues. Chism's lawyer, Denise Regan, said she would raise the issue of mental competency "if and when" she feels it is appropriate.

Students told police that Chism stayed after school the day the 24-year-old Ritzer was killed. One student who said she had also stayed after school to receive extra help that day said Chism appeared to become upset when Ritzer began talking about Tennessee.

Search-warrant documents made public last month described surveillance video that authorities said showed Chism following Ritzer into a school bathroom, wearing gloves and a hood, then later walking out of the bathroom alone.

A short time later, the video shows Chism pulling a recycling barrel through the school and outside, according to the documents. A recycling barrel was found near Ritzer's body. Authorities said she was sexually assaulted with a stick.

Chism is charged with murder as an adult but faces other charges in juvenile court. Authorities may seek to have all charges tried in one court.