The graffiti - on boards by the swimming pool at Storrington Primary School in Spierbridge Road - was discovered when staff returned after the Christmas break on Thursday.
Police say the graffitti had already been removed by the time they were informed of the incident.
A spokesman added:”Nothing was reported to have been stolen and there was no break-in reported to the premises.
“Anyone with any information can contact Sussex Police online at https://sussex.police.uk/appealresponse or call 101, quoting serial 805 of 04/01.”