At Mae Sai Prasitsart School in Chiang Rai province where six of the boys attend, all of the 12 boys were given a warm welcome back to school.
The ceremony was also marked with Buddhist prayers, according to Chiang Rai officials.
Dressed in their respective school uniforms, the boys were also given team shirts of Germany’s Bayern Munich football club by a club representative.
A dramatic 19-day search and rescue mission for the group, a local youth football team, has gained much attention, sympathy and admiration from around the world.
Many international football clubs have invited the group to come and see matches abroad following their dramatic rescue.
The group visited Tham Luang-Khun Nam Nang Non Cave, 1,000 kilometres north of Bangkok, on June 23.
They were trapped inside for more than two weeks after a flash flood blocked their only exit, leading to Thailand’s biggest-ever rescue operation which involved thousands of people from many countries.
After a successful rescue of all members of the group on July 10, the boys aged 11-16 recuperated at a nearby hospital for a week and then at home for another week.
Eleven boys, with an exception of 14-year-old Adul Sam-on who is a Christian, entered a nine-day monkhood as an act of gratitude for their rescue.
They left the monastery on Saturday.
Their coach, 25-year-old Ekapol Chantawong, the only adult in the group trapped in the cave, is expected to remain a monk for three more months.
A museum is being constructed near the cave to commemorate the rescue.