Harley Douglas, 14, was last seen at Boclair Academy in Bearsden, East Dunbartonshire.
The teenager, from Bishopbriggs, was wearing her school uniform - a black skirt and white short-sleeved shirt - and cream-coloured Converse shoes with studs.
She is described as 5ft 6ins, slim, with long, dyed blonde hair.
A Police Scotland spokesman said: "Harley is known to frequent the Kirkintilloch, Bishopbriggs, Torrance, Bearsden, Partick, Glasgow city centre, Renfrew, Erskine and Bishopton areas, but despite extensive enquiries there have been no sightings of her since Monday June 23.
"Police are becoming increasingly concerned for her safety and ask if anyone has seen her since Monday or know of her present whereabouts to contact Kirkintilloch police office on the non-emergency number 101."