VANDALS attacked Maclean High School in the early hours of Sunday morning, smashing 19 windows and causing thousands of dollars worth of damage.
The vandalism comes in the wake of a spate of thefts, where students' mobile phones have been stolen.
School principal Glen Brown said even though windows were smashed throughout the school, nearly all classes were able to proceed as normal yesterday.
Mr Brown described the damage as senseless destruction.
"In some cases it's big thick plate glass over one centimetre thick. It's pretty solid stuff and it takes some force to break them," he said.
"Nothing was taken, so they were not looking for anything, so it's a bit incomprehensible when it's just damaging things for the sake of damaging them."
Mr Brown said the damage was even more annoying considering the school did not suffer any attacks throughout the school holidays.
"I'm a bit surprised because we haven't had a lot of trouble here," he said.
"There was no vandalism at all during the six weeks of summer vacation."
Large rocks were apparently used in the attacks, as many were found near broken windows.
Windows were smashed in the science, music and art, special education blocks, one of the kitchens and the school hall.
"It's senseless, there's no logic to it and it doesn't make any sense," Mr Brown said. "It's a total waste of everyone's time and resources."
Maclean police are investigating.