RURAL schools perform better in the HSC the further away they are from larger competing schools, an analysis of NSW results has found.

The data presented to a public education conference in Canberra suggests that schools enrolling most of their local children produce a higher proportion of high-end results.

Chris Bonnor, the former head of the NSW Secondary Principals Council, said that rural comprehensive schools were the pioneers and last remnants of "fully inclusive public schooling".

"In rural areas we have living examples of schools which have been denied the alleged benefits of the free market," he said. "Competition has never lifted all schools for the benefit of all."

At schools in areas including Tumut, Glen Innes, Condobolin, Inverell and Mudgee, between 90 and 200 kilometres away from larger competing schools, more than 3 per cent of HSC results were above 90, based on a three-year average.

At schools in areas including Lithgow, Narrandera and Gundagai, which were 60 to 89 kilometres away from larger schools, about 2.8 per cent of scores were higher than 90. The proportion of scores over 90 at schools that were 40 to 59 kilometres away from competing schools was about 2.5 per cent.

However, the proportion of high-end HSC results fell to about 1.7 per cent at schools in areas including Uralla and Molong, which were within one to 34 kilometres of larger schools.