The victim has been named locally as 13-year-old Heather Still.
Emergency services were called to Whitecraigs railway station around 2pm on Tuesday.
British Transport Police have launched an investigation into the circumstances surrounding the death of the pupil, who is believed to have attended Mearns Castle High School in Newton Mearns, East Renfrewshire.
A police spokesman today said: "We are treating the death as non-suspicious but investigations are ongoing. Specialist trained family liaison officers are helping the girl's family."
Train services through Whitecraigs were disrupted for two hours immediately after the tragedy.
Paramedics were called to the railway station but the teenager was pronounced dead at the scene. Afterwards, stunned school friends left tributes on social media sites.