The incident happened at the government middle school in Rampur Bakhra village under Lalganj block.
District Magistrate Jitendra Shrivastava said the 27 school children were admitted to Hajipur Sadar hospital where all of them were stated to be out of danger.
The children complained of stomach pain and vomiting after taking mid-day meal which reportedly contained a dead lizard.
The DM said the District Education Officer has been directed to inquire into the matter.
Shrivastava said the left out food has been sent for test.
The incident has come close on the heels of death of 23 children after eating mid-day meal at neighbouring Chhapra school on July 16.