Mrs Tolley, who is believed to be the first Minister of Education to visit the school in its 48-year history, officially opened the building yesterday afternoon.
The 1300sqm complex includes a sports floor, changing rooms and two classrooms and its construction began two years ago, when former principal Dave Smyth was still at the helm of the school.
Mr Smyth stepped down from teaching last year after 33 years at Dunstan, the last 10 as principal.
"This has been a journey, but we're thrilled with the result," he said.
The school had never had its own gymnasium and instead used Molyneux Stadium, which was located in Molyneux Park, near the school.
Mr Smyth said there had been a flurry of building activity at the school in the past five years, after about 25 years with no new buildings.
A whare and a performing arts suite had been constructed and the library had just been transformed into a new administration block.
The Ministry of Education provided funding for the new gymnasium, through two grants.
"It's in an ideal place and will bring people back into the main area of the school," he said.
"Our sports teams finally have a home base.
"Being a rural school, we travel a lot for sport and now we have somewhere to host travelling teams when they come to us."
The facility would add to the variety of opportunities the school could offer to the community and to young people.
Principal Brent Russell said board chairman Grant Campbell and Mr Smyth were the main drivers of the project and it had been an immense task.
Mrs Tolley said the new building was a modern and practical facility.
"It has been designed for and caters for learning, not just functionality."
Dunstan had a reputation as a pioneer in the field of outdoor education and the list of successful sportspeople from the school were all involved in "outdoor" sports.
The gymnasium would help foster indoor sports so Dunstan pupils could also make their mark in those codes, she said.
