Introduction: Basic life support training in school age is a topical issue because, with adequate training, any person can help save a life., Methods: Cluster clinical trial with data collection through an ad hoc self-administered, semi-structured questionnaire. The target population encompassed the students aged 4-6 years enrolled in 49 educational centres. The centres were randomly allocated to the intervention or control group. The intervention group was trained with the RCParvulari® methodology, consisting of theoretical and practical training on the first link of the chain of survival. The control group only received theoretical training. We evaluated participants before and immediately after the intervention and between 3 and 12 months post intervention by means of the questionnaire. We assessed the acquisition and retention over time of the knowledge and skills covered in the training compared to previous trainings in both groups., Results: A total of 1327 schoolchildren (79% of the target population) participated. The level of knowledge acquired immediately after training and after 3-12 months compared to baseline was significantly better (P < .001) in the intervention group than in the control group, both in early recognition and contacting of emergency services (112) and in remembering the "mouth-nose-eyes" mnemonic., Conclusions: The RCParvulari® methodology significantly contributed to an improved ability to recognize a possible medical emergency, start the chain of survival by alerting an adult and call the 112 emergency number in students in the last year of preschool education., (Copyright © 2022 Asociación Española de Pediatría. Published by Elsevier España, S.L.U. All rights reserved.)