NSW should consider selective primary schools for its most gifted students and give them the same early intervention as students with special needs, according to a leading academic in gifted education.

Jae Jung, a senior lecturer in the University of NSW's school of education and a lead researcher of gifted education, said primary schools modelled after the state's 48 selective high schools could be the solution to Australia's "neglect" of its brightest students that is leading to its sliding performance at the international level.

"We're not taking care of gifted students at the lower primary level," Dr Jung said. "The earlier educational intervention is provided, the more likely their potential will be realised.

"These are the students who will find cures to major medical conditions and make a real difference to the lives of others, but they're the ones we're neglecting."

A spokesman for the NSW Department of Education did not rule out the option of selective primary schools and said that the department "is currently reviewing the Gifted and Talented Policy and the updated policy is expected to be released later this year".

Principals can already "create classes that best meet the needs of their community, this includes classes especially formed for high performing and talented students", he said.

However, the first formal chance for gifted students to enter special classes is in Year 5, through opportunity classes that separate the highest-achieving students for the final two years of primary school.

This year, 11,849 Year 4 students will compete for 1740 places when they sit the opportunity class placement test on Wednesday.

Dr Jung said more opportunity classes should be made available and expanded across all primary years.

"If there's political resistance to selective primary schools, we could have opportunity classes at all levels of primary school," Dr Jung said.

"Because gifted students aren't being identified, they're bored in the classroom and some become disinterested in school."

Layelle Etri, 11, who is in a Year 6 opportunity class at Blaxcell Street Public School, said she "wasn't really learning much" in her mainstream classes before Year 5.

"I wasn't being challenged," Layelle said. "I would finish work quite quickly and then help other kids or just read a book.

"I look forward to coming to school more now. Most of my friends want to become scientists and doctors, we all have the same goals, whereas my friends in my old school weren't interested in those things."

Dr Jung said that up to half of all gifted students in primary and high schools are found to be "underachieving significantly".

He said a major part of the problem is that teachers are not required to learn how to identify or teach gifted students as part of their pre-service training.

"Special education training has been mandatory since the early 1990s but nearly 30 years later, there's still no requirement for teachers to get trained in gifted education," Dr Jung said.

"Australia is an egalitarian society and there's always a focus on helping those with special needs, but we're ignoring students at the other end of the spectrum."