A group of top kids' authors, including Gruffalo writer Julia Donaldson, says extreme hunger leaves children struggling to read and write.
The children's laureate backs a global study that suggests children who are badly malnourished are 20% more likely to misread simple sentences.
The research was carried out by the University of Oxford for the charity Save the Children and looked at 7,300 eight-year-olds in four countries - Ethiopia, India, Peru and Pakistan.
Other top children's authors backing the campaign are Michael Morpurgo, Philip Pullman and David Walliams.
Justin Forsyth from Save the Children says: "poor nutrition is capable of seriously damaging a child's life chances before he or she even sets foot in a classroom".
The report says that even if the children have good schooling, the benefits of it get cancelled out if they're not eating well.