Pradyuman, a student of the Ryan International School, Gurugram, was found dead inside the toilet of school premises, with his throat slit on September 8.
As per sources, the probe agency has not recorded a statement of the minor in front of the Magistrate as of now.
The CBI also questioned the ex-employees of the school apart from teachers and students.
The murder case of the seven-year-old took a new dimension on Wednesday after the CBI trashed the probe by the Gurugram Police and gave a clean chit to the bus conductor, arrested on the charges of murder and sexual assault.
The CBI instead arrested a class 11 student of the Ryan International School.
The CBI then produced the accused juvenile before the Juvenile Justice Board and demanded his six-day custody.
The accused also confessed his crime in front of his father, the CBI told a juvenile court.
The juvenile court, however, granted only three-day custody with a rider that the accused can only be questioned from 10 a.m. to 5 a.m. only.
The probe agency also told the juvenile court that the juvenile's father was informed about his son's arrest. The accused was also medically examined on November 8 at 0330 hours at the Safdarjung Hospital.
The CBI has said the accused committed the crime in order to postpone the parents-teachers meeting and the exams.
Meanwhile, the victim's family has demanded that the juvenile student be tried as an adult and accordingly, be given a harsh punishment. (ANI)