Introduction: Under-nutrition remains a major public health concern affecting school-aged children by impairing growth, development, and academic performance. This study uses both the z-score system and the Composite Index of Anthropometric Failure (CIAF) to evaluate undernutrition among rural school children in Puducherry, India. Materials and Methods: A total of 792 children from six schools were assessed between November 2013 and January 2014. WHO Anthro-Software and EPI-Info 7 were used for analysis, with chi-square testing for associations. Results: Overall, 48.7% of children exhibited anthropometric failure, with underweight accompanied by wasting being most prevalent (18.7%). Underweight and wasting were significantly higher among males, while stunting showed no gender difference. Relying solely on weight-for-age underestimates undernutrition by nearly 10%. Conclusion: The z-score and CIAF systems provide a more comprehensive diagnosis of undernutrition by identifying children with multiple anthropometric failures, aiding better prioritization for intervention. © 2018 Elsevier B.V., All rights reserved.