Despite the lack of power, teachers are still continuing their lessons. Some classes sat outside in the sun, while others stayed inside with windows and doors open. Students were bundled up because it was chilly in the morning hours.
Clocks at the school were stopped at 11:50, the time authorities believe the thefts took place.
Thieves targeted multiple areas around campus, ripping copper from ground vaults and breaker panels. Police say some of the work required heavy tools to cut through the thick cables and a working knowledge of electricity.
"It's bothering that we do have criminals out there that would target educational institutions like this, but they don't necessarily see what they're hurting because they're long gone," said school safety officer Eric Vetere.
A school official said lunch would be provided for all the students, and a contractor was looking into restoring the power as soon as possible.
Anyone with information about the incident is urged to call San Bernardino School District Police at (909) 388-6130.