Arjun Rai, who was accused of buying the pesticide that got mixed with the food, was on the run after the July 16 tragedy. He surrendered Monday in the court of the chief judicial magistrate in Saran district, police said.
"Rai surrendered after the court issued a non-bailable arrest warrant against him and dismissed his anticipatory bail plea last week," a district police official said.
His wife, Meena Devi, was the principal of the government primary school at Gandaman village in Saran district when the children died. She was arrested a week after the deaths.
A first information report was registered against her on charges of murder and criminal conspiracy, police said.
A forensic lab report confirmed that traces of toxic insecticide were found in the cooking oil used for making food at the school, police said.