Matric learners have been studying on the grass outside the Hector Peterson Memorial Library in Lwandle, Strand, after electricity was cut during a burglary.
The library was burgled on Monday for the second time in two weeks.
Cages around the air-conditioning systems were damaged and cables stolen.
GroundUp reported in August that internet cables had been stolen from the same library, resulting in a lack of internet access for users for over a year.
"We are sitting outside because it's dark inside," said matriculant Steven Phambaniso, who was studying with his friends. "We cannot borrow books anymore because everything is off inside."
Another learner, Esihle Spani, said it was hard to study at home because of a lack of space and noise from family members. "It is difficult to focus at home; the house is small, and everyone is busy with their thing. This is the only library we have."
A librarian said the library could not be opened without electricity. "The alarm is off and we will not be able to monitor users when they walk out with books. There is only one security guard. This week the electricity was going to be fixed, then the second break-in happened."
Resident Zolile Witbooi said the children's future was at stake. "We need security 24 hours because the criminality happens at night. The learners need books for studying or they will fail."
Councillor Zahid Badroodien, mayco member for Community Services and Health, said he did not know when the library would reopen. "Electricity cable theft has affected the library since 11 October 2019. The library has since not been able to operate fully, but the library hall has been made available for students to study."
He called on residents to assist by reporting damages.
Captain FC van Wyk of SAPS said police were investigating.