The victims were on their way to school Friday when they were attacked by a group of 10 students from another high school in Kemayoran, Central Jakarta, the Jakarta Globe reported.
"The acidic water was in a white bottle, and [they] quickly threw it," one of the victims said. "Afterward they fled toward Senen."
Police said three of the victims suffered light burns to their necks, while the fourth victim suffered more serious injuries.
The acid attack was the second this month in Jakarta. High school student Ridwan Nur threw an acidic solution at bus passengers in Jatinegara, East Jakarta, injuring 13 people, officials said.
Wisconsin business offering 'therapeutic cuddling' forced to close
Couple calls 9-1-1 over missing hash browns; assault McDonanld's employees