Iron deficiency anaemia in infants can cause developmental problems. However, the relationship between iron status and cognitive achievement in older children is less clear. This study was undertaken to investigate the relationship between iron deficiency and cognitive test scores among school aged girls. Quasi random experimental research design was used. School girls aged 8 to 11 years from Banasthali residential school were selected purposively. Haematological assessment included estimation of haemoglobin (Hb), red cell indices, serum iron, total iron binding capacity (TIBC), serum transferrin saturation and serum ferritin. Psychological assessment was conducted to determine intelligence quotient (IQ), intellectual capacity, educational achievement. Among 111 children in the sample, 77% were anaemic. Serum iron, TIBC, transferrin saturation and serum ferritin were significantly lower in anaemic girls when compared with non anaemics. The former had lower IQ, intellectual capacity and educational achievement than those of their non anaemic counterparts. These three parameters had significant correlation (p<0.05) with Hb and serum iron. We demonstrated lower cognitive test scores among iron-deficient anaemic school age girls.