We conducted a study to determine the effectiveness of a 30-min hand-washing instruction among youths in kindergarten through fifth grade. Two months after implementing the instruction, we gathered survey data to assess knowledge gained and student behaviors. Results revealed that high proportions of youths in kindergarten through second grade (n = 90) were able to recognize various situations requiring hand washing and that majorities of youths in third grade through fifth grade (n = 172) tended to wash their hands at relevant times (e.g., after using the bathroom). Overall, we concluded that youths taught a 30-min hand-washing lesson reduced microbial counts on washed hands, maintained knowledge, and made positive behavior changes.