The Durrant Road fire was quickly put out before it could damage North Parmelia Primary School.
"Kwinana Police will, in conjunction with Education Security, be monitoring schools over the holiday period, targeting vandalism, trespassing and other crime," Officer in Charge Steve Thompson said.
"Damage and crime to schools affects the whole community and I would ask anyone living near schools to report suspicious behaviour to police on 131 444.
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READ NOW"Further, over the school holidays, parents should ensure they know the whereabouts of their children at all times and ensure they aren't engaging in offences or anti-social behaviour."
A Department of Fire and Emergency Services spokeswoman said one team from Hope Valley Fire and Rescue attended the scrub fire that was believed to be deliberately lit just before 6pm.
It was extinguished 20 minutes later.
The same night, Hope Valley Fire and Rescue put out a trail bike that was on fire behind a sand pile on Johnson Road in Wellard just after 7pm.
Investigations are continuing.