Background Automated external defibrillators (AEDs) have been widely distributed at schools in Japan. We have demonstrated that ventricular fibrillation accounted for 68% of nontraumatic sudden cardiac arrest (SCA) in schools, suggesting that a well-prepared medical emergency response plan (MERP) for schools would improve the outcomes of SCA patients. However, it is uncertain if the MERP has been well developed or implemented in Japanese schools. Methods and Results We conducted a cross-sectional study of schools in Osaka using a postal questionnaire. Survey items included type of school, number of students, school staff and teaching staff, number of AEDs used and the place of installation, cardiopulmonary resuscitation (CPR) training to school staff, MERP development and implementation, and the number of SCA cases they experienced. The response rate to this survey was 44% (764 of 1728 schools). Every school except for 4 have installed at least 1 AED. Thirty-six percent of schools, however, have not yet developed and implemented a MERP for SCA. Moreover, 49% of schools surveyed have not conducted a rehearsal training session for SCA in the previous 3 years, although 95% of schools provided CPR training courses to school staff. A total of 15 schools have experienced 16 presumed or actual SCA cases in the study period. Of the 15 schools, 6 schools reported that bystanders experienced psychological stress. Conclusions A MERP for SCA has not yet been fully developed and implemented in the schools surveyed in our study despite widely distributed AEDs and CPR training.