Ethical approval and consent to participate
The trial was approved with the written consent procedure to be followed by the Institutional Research Ethics review Board (IRB) in College of Medicine and Health Sciences, Arba Minch University with the reference number of IRB/154/12. The world medical association declaration of the Helsinki was followed in each step of the research. Official permission letter to conduct the research was submitted to district health offices and education offices in Dara Mallo and Uba Debretsehay districts. Support letters written by the respective education offices were given to each participating school and written consent was obtained from school head teachers. Written informed consent was obtained before data collection from the parents or guardian of children and it was documented in College of Medicine and Health Sciences, Arba Minch University.