To assess the relationship between severity of small for gestational age (SGA) and the risk of poor school performance, and to investigate whether adult stature modifies this risk.
1,088,980 Swedish children born at term between 1973 and 1988 were categorized into severe SGA (less than -3 standard deviations (SD) of expected birth weight), moderate SGA (-2.01 to -3 SD), mild SGA (-1.01 to -2 SD), and appropriate for gestational age (-1 to 0.99 SD). The risk of poor school performance at the time of graduation from compulsory school (grades