Background: The most visible effect of iodine deficiency (ID) is goiter, but the worst and much greater public health problem is its impact on the developing brain. Despite relatively increased attention to the consequences of ID on physical health, there are only a few studies on the influence of ID on schooling in Ethiopia.

Objective: The main objective of this study was to determine the effect of chronic ID on academic performance of school children in southwest Ethiopia.

Methods: This study was conducted on 652 school children selected from six primary schools in southwest Ethiopia. Using prospective cohort study design, 362 iodine deficient and 290 iodine sufficient children were followed for the difference in academic grade scores for a period of 18 months.

Result: Average grade score of children for both groups was 72.5%. Among iodine deficient children, about two-thirds (65.8%) performed below the mean grade score (X² (df), 46.86 (1), p<0.001). Both school absenteeism and dropout from school were significantly higher for iodine deficient children. For example, for a single day’s absence from a class, the average grade score declined by 1.1 points (β=-1.10, 95% CI, -1.52, -0.70).

Conclusion: Despite the efforts made by the Ethiopian government on universal salt iodization and other iodine deficiency disorder prevention programs for the last decade, many south Ethiopian children were unable to utilize their full academic potential due to chronic iodine deficiency.

Recommendation: The visible effect of iodine deficiency is goiter, but the worst scenario is its effect on developing brain. Therefore, iodine deficiency disorders prevention and control programs should focus on the effect of ID on the mental potential of children in Ethiopia.