The main purpose of this study was to assess the effects of daily physical activity on exercise tolerance ability using the six minute walk test in healthy female students. The participants in this field study were 252 healthy girls، 9-12 years old، studying in an elementary school in Tehran from March to June 2011. A three months daily physical activity protocol، with 15 minutes exercise per day، was designed as a curricular-based exercise intervention program. The six minute walk test was used as a tool to measure exercise tolerance ability before and after the intervention. Paired t-test، ANOVA and correlation tests were used when appropriate. The participants، with mean age of 10. 6 (SD = 1. 1)، formed different body mass index groups known as underweight، normal، at risk and overweight with 8. 3، 60. 7، 18. 7، and 12. 3% respectively. The mean of the distances moved along in a six minute walk test، before and after the intervention، increased from 833. 4 meter to923. 3 meter، indicating 10% increase and the difference was found to be statistically significant (P<0. 001). However، analysis of mean differences of the walked distances، before and after the intervention، showed no statistically significant difference for the body mass index groups (P> 0. 05). A 15-minutes daily physical activity could enhance the exercise tolerance of school-age girls; the activity، as an easy and inexpensive form of intervention، is recommended to students.