New Delhi, India (CNN) -- The school called it a meditation session in which students as young as five walked barefoot on shards of glass and smoldering coal.
Kalpesh Patel, director of the Riverdale Academy school in the Western Indian town of Surat, said the students' parents had given their consent for their children's participation in the fire-and-glass walk, aimed at boosting confidence levels.
Patel said the children were in a meditative trance during the program at a two-day summer camp.
"No one was injured and no one felt any pain," he said, adding that his own child was among the 80 participants.
The school has been holding such programs for some time, Patel said. The walk followed rock-climbing and river-crossing activities.
But Indian education authorities said they have launched an inquiry.
"The focus of our inquiry primarily will be to determine whether the school took permission from the parents or not," said Surat education officer K.R. Zanzrukia.
He acknowledged that the activity had been an annual feature at the school for several years.
The program, however, did not sit well with children's activists.
Sandhya Bajaj, a former member of India's National Commission for Protection of Child Rights, said school organizers should face criminal charges.
"This is clearly torture and cruelty," she said.
She rejected the school's claim that the activity helped build confidence among the pupils.
"This is no way to boost self-confidence," Bajaj said. "There are so many other ways to do that."