At least 60 children were taken ill after eating a mid-day meal served at a school in Behalolpur village in Uttar Pradesh's Moradabad District.
The children, who are undergoing treatment at the district hospital, had started vomiting after having the meal.
D K Gupta, Chief Medical Superintendent, Moradabad District Hospital, said: "Around 61 children have been brought here on Thursday out of which 37 have been given saline water. All the children are better now," he said.
The children had the symptoms of nausea and dizziness after they returned home on Thursday.
"I had puri and potato curry at school. When I reached home after school I was feeling dizzy and then I started vomiting," said Sushila, a student.
An enquiry is being carried out into the incident and action will be taken against those involved in preparing and serving the meal, officials said.
India runs a huge midday meal scheme for children, with 120 million signed up to receive one hot, nutritious meal free on every school day.
According to media reports, corruption has marred implementation of the scheme in some States. One report in 2006 said that in Uttar Pradesh the ready-to-eat food, was diverted to feed cattle.