Poor primary school performance is a risk factor for low high-school and university graduation, as well as poverty in later life. In this case-control study, the relation between a variety of physical, environmental and sociodemographic factors, and primary school performance was investigated. Grade one students with good and poor school achievement, from different socioeconomic levels were studied. A questionnaire about the sociodemographic characteristics and child's medical history, together with a Child Behavior Checklist, was filled out by parents. Physical examination, visual and hearing screening were performed. Blood count and blood lead levels were determined. Wechsler Intelligence Scale for Children-Revised (WISC-R) was performed to determine the IQ. A total of 177 students participated in the study. Stepwise logistic regression revealed an independent positive relation between duration of study (OR, 2.69; Cl, 1.19-6.05; p = 0.016), maternal education (OR, 1.47; Cl, 1.14-1.87; p = 0.002), full scale score of WISC-R (OR, 1.08; Cl, 1.03-1.3; p = 0.002) and school performance. Multinomial logistic regression revealed that the risk of having a below average full scale WISC-R score was higher among children having a hearing loss, uncorrected vision loss, heating house with stove, cigarette smoking of both parents, and low paternal education (less than 8 years). The chance of having an above average full scale WISC-R score was lower among children whose either parent smoked cigarettes, height-for-age percentile was below 10, and maternal education was less than 8 years. Policies for increasing male and female education, growth monitoring, appropriate feeding (breastfeeding and weaning), well-baby and child followup and clean environment (indoor and outdoor) will not only promote the physical health but also promote the cognitive development of the new generations.