The incident happened over the weekend, between 17:00 on Friday 13 December and 08:00 on Monday 16 when staff discovered the damage.
It’s alleged a number of educational posters and playground toys were destroyed after being set alight, while storage lockers which had been knocked over were left damaged.
Guernsey Police say the investigating officers would like to speak to anyone with information relating to the incident, which happened in the reception year group playground at St Martins Primary School.
Witnesses should call PC 161 Ormrod on 725111 or Crime Stoppers anonymously on 0800 555 111.
Pictured: Inset – St Martin’s Primary School.