Background: School children pass through great physical and mental changes, which affect both their growth and school performance. Childhood malnutrition is a major concern in developing countries. Aim of the study: This study aimed to determine the change in the knowledge of children's mothers at school age in ElothmanyaVillage- El Gharbyia Governorate after an interventional program. Patients and methods: This study targeted two groups: The first group included obese children aged 8 to 15 years old and the second group included underweight children aged 7 to 16 years old using questionnaires, educational tools and model kitchen. Results: In obesity group, mothers' age ranged from 23 to 46 years with mean of 32.3 ± 5.7. Most of them were housewives. Most of fathers were workers and farmers in both groups. Attendance of mothers of obese children was as follows; 41.3% for once, 28.3% for twice, 17.4% for 6 times. Mean age of obese children was 10.8 ± 2.4. Mean BMI was 27.8 ± 1.7 and ranged from 26 to 34. Knowledge of mothers generally improved with average of 33.3% regarding obesity. Knowledge regarding obesity complications was found to be the most improved item when comparing it before and after intervention. In underweight group, Mothers' age ranged from 24 to 52 years with mean of 36.7 ± 6.1. Attendance of mothers of underweight children was as follows; 29.5% for once, 32.1% for twice, 14.1% for 3 times, 11.5% for 4 times, 6.4% for both 5 and 6 times. Mean age of Underweight children was 11 ± 1.9. Mean WAZ score  was -1.8 ±0 .8 and ranged from -3.09 to -1.02. Knowledge of mothers generally improved with average of 37.3% regarding underweight. Knowledge regarding Number of meals was found to be the most improved item when comparing it before and after intervention. Conclusion: These findings indicate that establishing interventional measures to improve knowledge in mothers and body mass index in children, is highly recommended.