A SYDNEY private school's investment in Aboriginal children is starting to pay off, with dramatically improved literacy and numeracy results.

St Andrew's Cathedral School in the central business district established a special school called Gawura for Aborigines just under two years ago in a spare classroom on its rooftop.

The school, established with donations, has reached its maximum number of enrolments of 25 pupils in kindergarten to year 6 for this year and next.

A snapshot of results for this year's first national literacy and numeracy tests shows the year 5 Gawura pupils achieved results in writing that bettered the state average and were less than one point below the school average.

Reading results were below the state average but well above the state average for indigenous students. Overall literacy was 491 points compared with the state average of 497.4.

The school's headmaster, Phillip Heath, said he was still concerned about numeracy test results that remained well below the state average for all students and those of indigenous background.

Overall, numeracy results were 411.6 compared to the state average of 489.1 for all students and 426.8 for indigenous students.

Mr Heath said that when students first arrived at Gawura, they were one to two years behind the average performance of other NSW students.

The NSW Government is aiming to lift the performance of all Aboriginal students to meet the state average.

Four of the Gawura students will enter high school at St Andrew's next year where they will continue to gain extra support.

While the Gawura children join other school children for cultural and sporting activities, Mr Heath said he had been criticised for teaching them separately from the others and creating a small "apartheid" at the school. But he argues that this was necessary to give the Aboriginal students the level of individual attention they needed to improve their results.

By high school age, it was expected that the Gawura students would be confident enough to join the rest of the school in mixed classrooms.

"They are really proud of who they are and they haven't lost their cultural identity," Mr Heath said. "They haven't had a 'whitefella' culture imposed on them.

"The children's engagement in learning has been really exciting. They belong to the school and the school belongs to them."