Mana College in Wellington will get a $15 million revamp.
The Government cash injection was announced by the Education Minister Chris Hipkins at the school today.
Mr Hipkins said the college will get a new library and administration block as well as several new classrooms.
"Plans include replacing the hall roof, demolishing up to 21 classrooms and rebuilding 17 larger flexible spaces,” Mr Hipkins said in a statement.
He said the college has had to make do with tired classrooms and leaky buildings for too long.
"Substantially more investment is needed, on top of the announcement in mid-2017 because of the school’s rising roll, and this growth is expected to continue as further housing developments are completed in the area, Mr Hipkins said.
Work is expected to start in the new year.