The Napthine government paid elite private school Scotch College $5.4 million for a thin strip of land, taken for a road-widening project, that was previously valued at just over $1 million by the state's Valuer-General.

The payment was made by VicRoads in October last year.

The sound barrier and South-Eastern Freeway over a section of Scotch College land for which the state government paid $5.4 million in a compulsory acquisition.

The government's road authority in 2008 used its compulsory acquisition powers to take a 2.8-metre-wide and 400-metre-long sliver of land from the Hawthorn boys' school.

The land was taken in order to add a lane to CityLink, which runs alongside the school.