Perth Modern School, which started educating elite students in 1912, is back where it started - ranked as one of WA's top schools.
The school, which ended exams to pick the brightest students in 1958, started taking Year 8s based on their abilities again in 2007.
Education Department director-general Sharyn O'Neill said she now expected Perth Modern to be "among the best" every year.
"If you're selected as gifted and talented, you're among the top 2 per cent, so you've got to expect them to be there," she said.
She said the school had some "seriously clever" students who "eat study, they are so dedicated, so passionate about excelling".
Ms O'Neill said it could be argued that private single-sex schools that ranked in the top five, year after year, were also selective because their students were from privileged backgrounds, the main predictor of academic success.
Perth Modern associate principal Val Furphy said the whole school was delighted with its "fantastic achievement" after years of hard work and dedication from teachers, students and families.
Year 12 graduate Max Carter, who topped the State in ancient history, said the school's achievement was well deserved.
"It was an honour to attend Perth Modern School with a group of like-minded people who were always eager to help and support each other," he said.