The three officials were part of the Special Investigation Team (SIT) that was formed for questioning.
Pradyuman, a student of Ryan International School was found in a pool of blood, with his throat slit, inside the school premises on September 8 last year.
Following his death, Gurugram Police arrested the bus conductor on the charges of murder of the child.
The case was later handed over to the CBI, who gave a clean chit to Ashok and held a class 11 student responsible for the murder.
Last month a Child Special Court also acquitted bus conductor Ashok Kumar in the murder case