Methods This research is a descriptive–analytic study which was carried out on 665 primary school age children in Yasuj (1384) in two equal groups as smoker and non-smoker families (sample and control) after equalization of these two groups with attention to age, sex and parent’s occupation, by Rieven’s test for evaluation of IQ and by reference to their written average for educational advance evaluation.

Results This study revealed that the chance ratio of above average intelligence in non-smoker families was 2.5 times more than smoker families. In educational advance the student’s written average in non-smoker famillies was 0.65 more than smokers. Also, good average (>17) in non-smoker families was 15% more than smoker families; these findings are significant. The number of above average intelligent children in males in non-smoker families was 12.9% more than smoker families. But this difference was not significant in females.

Conclusion The findings of this study revealed that passive smoking has a significant harmful effects on educational advance and IQ, especially on high grades. Due to this fact it appears essential to educate parents about smoking daqngers at home through mass media.