Action News has learned the teenage boy will be sentenced in two weeks.
The unidentified 14-year-old remains at a juvenile detention center. His mother also faces charges in the case.
The Richboro teen admitted to charges of terroristic threats and possession of a firearm by a minor during a juvenile court hearing last week, said Michele Walsh, chief of the juvenile division for the county district attorney's office.
The freshman had been taken into custody Dec. 20 after students at Council Rock South High School alleged he made threatening statements. Police later recovered a pair of World War II-era firearms from his nightstand.
Authorities said the teen's mother, Lizabeth Donohoe, 50, had given her son access to the 9 mm semiautomatic handguns, which belonged to her father. The weapons were unloaded but functional when police found them, authorities said.
Donohoe was charged with counts including possession of a firearm by a minor and endangering the welfare of children. A preliminary hearing scheduled for Thursday was delayed until next month.
Donohoe knew nothing about the threats, said her attorney, Louis Busico.
Council Rock School District is headquartered in Newtown, a community with the same name as the Connecticut town where a gunman killed 20 first graders and six school staff members on Dec. 14.
The teen's high school is in nearby Holland.