COURTENAY Gardens Primary School was targeted by burglars on the weekend for the second time in a month.
Offenders forced entry to one of the portable classrooms at the Cranbourne school between 6am and 7am on Sunday.
An Acer computer valued at $500 was stolen after thieves entered through a window to the classroom.
Three other computers were also moved but were not taken.
Police said it appeared the alarm was activated twice.
Security attended on the first occasion but reportedly did not see anything before the alarm again activated later in the morning.
Police said the same classroom was hit just a couple of weeks ago and a projector was stolen.
Representatives from the school did not want to comment on the incident.
Anyone with information about the two events is urged to contact Senior Constable Steve Regnier at Cranbourne CIU on 5995 4577.