The effectiveness of dissemination of public-access automated external defibrillators (AEDs) has been well established for adults, but not for children at the population level. We obtained out-of-hospital cardiac arrest (OHCA) data between January 2005 and December 2014 from a nationwide OHCA registry of Japan. Our study subjects were OHCA cases aged 6 to 17, involving attempted resuscitation by emergency medical service personnel or by bystanders. The primary outcome measure was 1-month survival with favorable neurological outcome after OHCA. We evaluated trends in the proportion of OHCA cases receiving shocks by a public-access AED and outcomes after OHCA over the 10-year study period. Prehospital factors associated with 1-month survival with favorable neurological outcome were also evaluated. During the 10-year study period, a total of 5,899 OHCAs occurred in school-age children, and 1,452 (24.6%) were of cardiac origin. The overall OHCA incidence rate in school-age children was 4.2 per 100,000 people per year. The proportion of patients with OHCA who received shocks by a public-access AED increased significantly during the study period (0.1% in 2005 and 6.4% in 2014, p for-trend <0.001). Accordingly, the 1-month survival with favorable neurological outcome improved significantly (5.3% in 2005 and 9.0% in 2014, p for-trend <0.001). In multivariable analysis, receiving shocks by a public-access AED was significantly associated with improved outcomes (adjusted odds ratio 2.13, 95% confidence interval 1.43 to 4.15; p <0.001). In conclusion, the significant increase in receiving shocks by a public-access AED was followed by a substantial improvement in patient outcomes after OHCA in school-age children in Japan.