PURPOSE: This study was conducted with the objective of estimating the prevalence of defective vision among school children. Children with defective vision refer to nearby eye hospital for further diagnosis and treatment to prevent long term visual disability. MATERIALS & METHODS: This study was conducted in school children of class first to tenth of selected private and government schools of Jhunjhunu district from Jan to August 2011. Total 2,490 school children from both private and government schools were included in which 1,430 were boys and 1,060 were girls. To detect the eye diseases following tests were adopted in school premises-- 1) distant vision with the snellen's chart, E chart. 2) Those children who had defective vision (VA<6/9 in either eye) referred to kedia eye hospital Chirawa for further investigation& proper treatment. 3) Eye examination by torch light. RESULTS: we found 474[19.03%] prevalence of defective vision in school going children. Bilateral defective vision was found in 402[84.81%] children. Unilateral defective vision was found in 72[15.18%] children. All the children with defective vision referred to eye hospital chirawa. 307 children with bilateral defective vision and 52 children with unilateral defective vision came to eye hospital Chirawa. The causes of B/L DV were refractive errors in 302[98.37%]; corneal opacity and scars 03[00.97%], squint 02[00.65%]. The causes of U/L DV were refractive errors 30[57.69%], corneal opacities & scar 14[26.92%], strabismus 01[01.92%], cataract 02[03.84%], others 05[09.61%]. INTERPRETATION: The results of the study show that most common cause of defective vision in school children was refractive errors. So by these school health program we can early detect and treat ocular problems and minimize long-term visual disability.