Principal Sunirmal Chakravarti and three teachers -- Garnian, Partho Dutta and David Raun -- were arrested on Monday morning, Joint Commissioner of Police (Crime) Damayanti Sen said.
The class VIII student had killed himself on February 12, four days after being caned by the principal. He got the caning along with two other boys for playing truant, the principal had said.
Following his death, Rounjavit's father had filed a complaint against the school principal and teachers for subjecting his son to corporal punishment.
Describing the arrest as a "breakthrough", Rounjavit's father Ajay Rawla said they should be dealt with firmly and an example set so that other children are not ill-treated.
Rawla said he was very "grateful to god and the authorities for not letting this being swept under the floor".
"All that we are praying for is that those who tormented our child and treated him so badly should be dealt with as per law and an example must be set so that no other child is treated this way," he said.
The National Commission for the Protection of Child Rights, an autonomous body under the central government, had conducted an inquiry in June that found the school and the teachers guilty and had recommended suspension of the accused.
NCPR Member Ashok Agarwal said, "There was a clear linkage between the caning of the child and the suicide committed by the child. Therefore, this (the arrest) should have happened much earlier. It is better late than never".
The principal had, earlier this year, apologised for caning the student, saying it was a mistake.
However, he said the caning should not be linked to the death of the student as it was "stretching it a bit too far".
Denying allegations that the boy was caned so hard that the stick broke on his back, Chakravarthy had said he had given Rouvanjit two "mild strokes".
Chakravarthy had said Rouvanjit had been hauled up for bursting stink bombs in the classroom. He was issued a note and had been asked to bring his father to school.
Asked about the arrests, Michael Shane Calvert, vice president of the school's alumni association said, "It is a very sad day for Martiniere. We do appreciate that life is precious but linking the caning to the suicide will have to be looked into carefully."
"We still need to be careful about the impact that this is having and will have on the way students react to the disciplining because already there have been adverse reactions in the school and disciplining will be a problem. We need to look at ways of disciplining children through constructive measures."
