Police had a torrid time controlling the protestors and their repeated pleas to calm down failed to have any impact.
The siege was later lifted after Sarkar formally put down her papers.
Meanwhile, Chief Minister Mamata Banerjee called up the bereaved family assuring action.
The National Commission for Protection of Child Rights also took up the matter and asked the state government to initiate a probe.
"The chief minister today called up Oindrila's mother and expressed shock and grief over the girl's death, and assured proper action," the victim's uncle Alokesh Das said.
State Education Minister Bratya Basu later visited the family and promised strict action against the guilty.
"We have already ordered a probe. All those involved in this will be strongly dealt with. But this hooliganism which is going on in the school is completely unacceptable. This should be stopped immediately," said Basu.
School authorities maintained Oindrila did not inform them about being locked up, but her parents rubbished it. A school teacher Kajari Pal said the minor had tried to inform her about the incident.
"She was trying to tell me that something wrong had happened with her, but could not explain properly. So I asked her to bring her parents. But unfortunately she fell ill and eventually died," said Pal.
Yet to come to term with their loss, Oindrila's parents demanded punishment for those involved.
"If those responsible for taking away my girl are punished, we'll be able to live in peace. Moreover, action will ensure such incident do not recur and a precious life is not lost," said Santanu, the girl's father who expressed his happiness over the principal's resignation.
"There were several complaints against her (principal) and I am relieved that she has quit," added Santanu.
The family is also contemplating legal action against a city based private nursing home where Oindrila was admitted before her death, for alleged medical negligence.
