The objective of this systematic review was to determine the effectiveness of school feeding programmes in improving physical and psychosocial health for disadvantaged school pupils. Early malnutrition and/or micronutrient deficiencies can negatively affect many aspects of child health and development. School feeding programmes are designed to provide food to hungry children and to improve their physical, mental and psychosocial health. This review included eighteen studies; nine were performed in higher income countries and nine in lower income countries. In the highest quality studies (randomized controlled trials (RCTs) from low income countries, children who were fed at school gained an average of 0.39 kg more than controls over 19 months; in lower quality studies (controlled before and after trials (CBAs)), the difference in gain was 0.71 kg over 11.3 months. Children who were fed at school attended school more frequently than those in control groups; this finding translated to an average increase of four to six days a year per child. For educational and cognitive outcomes, children who were fed at school gained more than controls on math achievement, and on some short-term cognitive tasks. Results from higher income countries were mixed, but generally positive. For height, results from lower income countries were mixed; in RCTs, differences in gains were important only for younger children, but results from the CBAs were large and significant overall. Results for height from high Income countries were mixed, but generally positive. School meals may have small physical and psychosocial benefits for disadvantaged pupils.