Five boys have been charged after the serious assault of a 20-year-old man at Stirling Train Station on Thursday afternoon.

The victim remains at Royal Perth Hospital in intensive care with head injuries. He is in a critical condition.

Police said it was believed the group of boys were all wearing their school uniform at the time of the incident.

The 'school boys', aged 14 to 16, were charged with aggravated robbery and acts intended to cause grievous bodily harm.

The assault victim is in a critical condition.CREDIT:ERIN JONASSON

Mirrabooka Detectives would like to speak to anyone that may have seen the incident or the group of students in the area around the time.

They believe there was "some type of incident on a bus travelling to the station, prior to the assault" which may be linked to the assault at the train station.

They were on bus 998, travelling from Nedlands to Stirling Station.

A sixth boy was released without charge as police said he did not participate in the incident.

Anyone with information is asked to contact Crime Stoppers on 1800 333 000 or report online at crimestopperswa.com.au.