Nearly one in five teachers says they have seen an increase in the number of children coming to school hungry.
The Irish Times cites a study which polled more than 500 primary and secondary teachers - with nearly four in ten saying they had brought food in to feed a hungry child.
Up to 19% of teachers said they saw hungry children every day, while one in three had seen kids fall asleep for want of food.
The 'Lost Education' study, commissioned by Kellogg, says that Teachers believe children who come to school hungry are losing an average of 57 minutes of learning time each day - that is six weeks of learning time over an academic year.
Kellogg’s Ambassador Catherine Fulvio said: "Every child deserves to start their day with a nutritious breakfast, but the reality is that many children across the country are missing out in the morning.
"Hunger in the classroom is a problem that will impact the prospects of the current generation if we don’t do something about it now."
Half of respondents believe that children arriving to the classroom hungry are more likely to have issues socialising, while 71% think hunger in the classroom can lead to behavioural problems.
Fergus Finlay, Chief Executive of Barnardos, who are starting a new partnership with Kellog, said: "We provide breakfast to children attending Barnardos services and in our Breakfast Clubs in schools to support children’s attendance and participation in education.
"By ensuring children have a nutritious breakfast each morning, we are helping them to concentrate throughout the day, enabling them to learn and achieve their potential in life."