Adelaide's newest and most spectacular high school has officially opened, with about 350 Year 8 and 9 students walking through the door as the school holidays finish.

Considered the first cohort enrolled in the $100 million Adelaide Botanic High School, the Year 8 intake is already at capacity and will fill the senior grades over the coming years along with the Year 9s.

The school will eventually house 1,250 students, including Year 7s from 2022 when public high schools in South Australia (currently Year 8 to 12) shift in line with interstate models.

The impressive view from the new school's foyer. ( ABC Radio Adelaide: Laila Ferrier )

Principal Alistair Brown told ABC Radio Adelaide that the school had been designed very differently to those in the past, operating as a "vertical school" with a lot of light, open spaces and classrooms with little privacy.

"There's a lot of visibility, a lot of glass, and it's really de-privatised the practice of teachers," he said.

"It also means our students are very well connected, so instead of traversing a long distance horizontally to go from one space to another, they can actually move, under supervision, to different spaces and work within a learning precinct on a particular floor."

Located on Frome Road across from the University of Adelaide, the school has Botanic Park and Frome Park at its door, with students to utilise nearby ovals leased from the university for sport activities.

"It has been very cleverly designed in that the school is about 1.5 metres above the ground, so to actually come into the school you physically have to step up to the school, so it creates a natural boundary," Mr Brown said.

The cafeteria boasts modern architecture and concepts. ( ABC Radio Adelaide: Laila Ferrier )

School zone shared with Adelaide High

The new school shares an expanded intake zone with Adelaide High School and offers a specialist entry program in health and sciences.

Education Minister John Gardner said about 20 students a year would be able to take advantage of the program, with the rest of its 200-a-year intake to come from within the zone.

"At Year 9 there's fewer students this year, but you'd expect that given this is a cohort of students that already started at other schools last year," he said.

"But in five years' time we expect this school definitely to be at capacity.

"This cohort is going to set the benchmark for [the school's] culture into the future and I'm very confident."

Adelaide Botanic High School was signed off by the former Labor government, although the Liberal Party had been arguing for a second CBD high school several years, with its preferred location to be in the CBD's west near Adelaide High School.

"This is a great site. I think they [Labor] were about five years too late but they got there in the end," Mr Gardner said.

An amphitheatre-style classroom inside the new high school. ( ABC Radio Adelaide: Laila Ferrier )

Opposition Leader Peter Malinauskas said there was a "degree of satisfaction" inside the Labor Party following the school's opening.

"And [former education minister] Susan Close should feel an enormous degree of satisfaction today," he said.

Students back to school

Across South Australia, about 271,000 students went to school today, including about 17,000 pre-schoolers.

Inside 513 public schools across the state, 114,400 children were going to high school and 61,600 to primary school.

Some 95,000 students will attend private schools, although many are enjoying an extra day or two of holidays before starting.

There are 13,200 educators and staff in the private sector and 30,000 in the public system.

Mr Gardner said the Government was spending $100 million each for new high schools in the northern and southern suburbs, while a school was being built in Whyalla to replace ageing infrastructure across three schools.

He said there was also money for capital works upgrades in about 100 other schools over the next three years.