Having played host to voters and sausage sizzle enthusiasts on Saturday, the school was hit by vandals sometime between 9:15pm that evening and 1pm Sunday, police said.

It is understood at least a dozen windows were smashed and classrooms partially flooded after fire hoses were turned on overnight. There were also reports of faeces smeared in rooms.

On Monday, year 10 students had been relocated to Dickson College, where they are expected to stay for the rest of the week.

A spokesman for the ACT education directorate described the incident as serious, resulting in broken windows and "significant water damage". The cost of repairs had yet to be determined as of Monday evening.

"The directorate is working closely with the school not only in repairing the damage caused by this incident, but also generally in looking at strengthening measures to minimise this reoccurring," he said.

In a letter to parents, Dickson College principal Craig Edwards said the school had capacity to room the extra Lyneham students without disruption to its own timetable.

It is the latest in a string of vandalism attacks on Canberra schools this year, including an attack over the summer holidays which saw a tractor used to wreck destruction on an oval at Gold Creek Primary.

A Catholic school took to social media last week for help tracking down three vandals who smashed windows and glass doors at their Gungahlin campus the previous weekend.

Canberra police said that, while they had not set up a specific taskforce to tackle school vandalism, they regularly patrolled schools to prevent crime and worked closely with the directorate.

"Additionally, ACT Policing is intelligence informed and uses this information to prioritise and allocate our workforce to best serve the people of Canberra," a spokesman said.

In the past four years, government figures show vandalism against public schools has cost ACT taxpayers more than $1 million to clean up.

While incidents have fallen in the past decade with the roll-out of more high-security fences around campuses, this year looks on track for another large clean-up bill.

Twenty-nine incidents were reported in just the first three months of 2019, more than a third of the total recorded last year.

The directorate has urged Canberrans to view their public schools as community assets to be proud of, rather than vandalism targets.

Police said anyone with information about the Lyneham High incident should contact Crime Stoppers online or on 1800 33 000, quoting reference number 6397946. Information can be provided anonymously.