Background: Children's overweight and obesity have increased in Western societies, including Israel. Childhood is an important time for shaping healthy habits. Purpose: The purpose of this study was to evaluate the effectiveness of a healthy lifestyle intervention on health knowledge, behavior, and anthropometric measurements. Methods: A total of 396 fifth- and sixth-grade children, from 2 religious and 2 secular schools, participated in a nonrandomized controlled trial during the 2011--2012 school year. Intervention group were given an extensive educational program focusing on eating habits and physical activity. Results: Overweight and obesity decreased significantly within the intervention group (from 25% to 17.9%, P = 0.04), without a significant change in the control group (from 20.5% to 17.6%, P = 0.12). Religious children had double the risk of being overweight or obese (odds ratio [OR] = 2.10; 95% confidence interval [CI], 1.15-3.73; P = 0.02). Knowledge was improved in both study groups (P < 0.01), with no difference in health behavior scores at the beginning (P = 0.59) or end (P = 0.36) of the year. Discussion: Health Education during fifth and sixth grades improved children's weight and health knowledge but not healthy behavior. Translation to Health Education Practice: School-based healthy lifestyle educational programs are important for primary prevention and weight management. A AJHE Self-Study quiz is online for this article via the SHAPE America Online Institute (SAOI) http://portal.shapeamerica.org/trn-Webinars.