There are several reasons why Indonesian schools start early and end early:
Climate: Indonesia is a tropical country with a warm climate, so starting school early allows students to avoid the hottest part of the day.
Afternoon activities: Many extracurricular activities such as sports, music lessons, and religious education, take place in the afternoon, so having school end early allows students to participate in these activities.
Traffic congestion: Jakarta and other major cities in Indonesia experience heavy traffic congestion, so starting school early helps students avoid getting stuck in traffic on their way to school.
Cultural factors: Indonesian culture values punctuality and discipline, so starting school early instills these values in students from a young age.