Clyde Primary School has been rocked by news it is the custodian of a 4.5 billion-year-old meteorite.

Principal Maurie Richardson said the school had received word from Museum Victoria that an 85kg rock on display at the school is a fragment of Cranbourne's world-famous meteorite shower, the Cranbourne Leader reports.

Mr Richardson said when he announced the news over the PA system a huge cheer rang out across the school.

"The kids are really excited about it,'' Mr Richardson said. "We've had it on display at the school for two months, waiting for the test results.

"They feel like it's their rock, in a way. We've lovingly named it Clyde.

Museum Victoria Natural Science Collections manager, Dermot Henry, said it was an exciting find, with just 16 meteorites ever found in Victoria.

"We get a lot of rocks brought in that people think are meteorites. But there have only been four in the last 25 years that have turned out to be meteorites,'' Mr Henry said.

Mr Henry said nobody knew when the meteorite fell to the earth, but that testing showed it was about 4.5 billion years old.