A former president of the Secondary Principals Council says the selective school system is a form of apartheid.

Chris Bonnor is concerned that students who do not have access to selective schools are being disadvantaged.

He says there will be a huge social costs if students from inclusive schools are allowed to fall behind those attending selective schools.

"What we are doing in our secondary education in particular is we are separating out kids not only on the basis of academic ability, but on social background", he said.

"This issue not only relates to selective schools, it relates to schools generally that are able to select, substantially or even in a minor way, the students that they teach."

He says online selective schools that reach out to students wherever they are should be expanded, and inclusive schools should get a boost in funding.

"If you favour the advantaged and increase opportunities for them and you end up with the less advantaged falling behind, there are serious national, social and economic costs for any country or system that does that," he said.

"We're increasingly complaining in Australia about our long under-perfoming tail, and one of the reasons is that far too many of our schools are now, to one extent or another, selective."