Taking suo motu cognizance of the case, including the vandalism in the school that followed the girl's death, the state human rights commission asked the home secretary to task an additional director general of police to hold a probe.
Oindrila Das, a Class 5 student at the Christ Church School at Dum Dum in North 24-Parganas district, died Sep 11, a week after she was allegedly locked up inside the school toilet by some of her seniors who demanded money from her as part of ragging.
A day after her death, hundreds of people - mostly parents and guardians - ransacked the 131-year-old school, and forced principal Helen Sircar to resign. Hours later, she was arrested.
Sircar Wednesday virtually accused police and the mob of colluding during the vandalism.
"I wasn't arrested on my own like that. I was forced to court arrest by police and the mob," Sircar told mediapersons here.
"Given the circumstances, considering the safety of my teaching and non-teaching staff, I gave in. I didn't resign voluntarily. The police under instructions from the mob forced me to resign," Sircar said.
A court has granted bail to the principal, who was booked under several non-bailable charges following a police complaint by the girl's family.
Sircar criticised police for inaction and said officers were present during the entire episode when mobs ransacked and vandalised the school and the principal's office.
"We had called them to offer protection to us but they came after quite a while. They were present during the entire time the vandalism was going on. They acted according to what the mob told them to do. I don't want to recall the incident. Every moment was traumatic," said Sircar.
Over a dozen people have been arrested so far for the vandalism.
Ruling out suicide in case of Oindrila's death, Sircar said the alleged ragging "has not been proved".
Sircar condoled Oindrila's demise and said she would visit her bereaved parents "when the time is right".
Oindrila's father Santanu Das welcomed Sircar's proposition to visit the family but stressed on vigilance on her part to prevent such episodes from recurring.
"No one is taught to bully or rag...it is very unfortunate that it happened. I want the three students to be identified and marked for this behaviour. The governing bodies and committees should probe the matter," the grieving father of Oindrila told IANS.
"She is always welcome. But I request she should be alert...out of 100 students not all are bad...only some may go off-track...so one has to be careful," Das said as he broke down.
Yet to come to terms with Oindrila's death, Das and his family fervently hoped teachers developed an understanding of the students they mentored.
Das fondly recalled Oindrila's affinity towards her teachers.
He added, "... My daughter was very fond of her teachers... she had bought gifts for them to distribute in the upcoming pujas."
The West Bengal Human Rights Commission expressed "serious concern" over the events and directed the state home secretary to order a probe.
"The investigation will include death of the student, vandalism of the school by guardians and outsiders, police inaction and the principal's arrest," said a WBHRC official.
The Calcutta Diocese of the Church of North India, which runs the school, has announced that over 1,000 Christian-run schools will observe Sep 19 as a "black day" and remain shut.
The West Bengal Association of Christian Schools has set up an independent inquiry committee to look into all the allegations and find out the truth.
The probe will also decide when the school would reopen and whether Sircar would be reinstated as principal.