According to research by the Children's Society charity, more than half of the 2.2 million children living in poverty in England miss out on a free school meal every day.
Around 700,000 of these are not entitled to one, and a further 500,000 do not take them up because a fear of being stigmatised, the charity said.
Matthew Reed, chief executive of The Children's Society, said:
This report sets out shocking evidence of just how much hardship teachers up and down the country are witnessing in classrooms day in, day out.
Something is going badly wrong when teachers themselves are having to feed children.
Every child in poverty should be given a free school meal. Free school meals are key to moving children out of poverty and vital to helping them flourish.
More top news
Too many patients who undergo emergency bowel surgery are dying because of inconsistent care practices, health experts have warned.
A report by a think-tank that claims more than half of households take more in benefits than pay in tax has been condemned as 'spin'.
The Education Secretary has set her sights on 'coasting' schools that have "fallen under the radar" with plans to force improvements.