The Department of Education is surveying the community to find out its views on the proposal,following calls for another co-ed public school option in a region dominated by single-sex private schools.
The idea is supported by Randwick Boys'High School's principal - who originally floated it - and its P&C committee. But the girls'school - which has been told it would not be affected by any demographic change next door - is opposed.
An email sent to parents by the school last month,signed the"The Randwick Girls'High School Team",said staff had sent two letters of objection to Education Minister Rob Stokes.
They said staff were"gravely concerned about the ability to continue to provide an outstanding and empowering education to girls in the eastern suburbs as there could be a reduction in the resources and courses/electives at the school.
"The letters[to Mr Stokes] have also outlined that ... there are already three co-educational schools in close proximity to Randwick Boys,which have capacity to take on more students. It is neither essential nor productive to turn the only boys'school in the eastern suburbs into another co education facility."
The email urged the girls'parents to have their say."In having your say,you are casting a vote against the proposal,"it said.
Parents from other schools in the area,who spoke on the condition of anonymity,said many were upset about the letter as they felt the school was trying to sway parents'views. The boys'school has not issued any similar correspondence.
The issue of a co-educational high school has become a politically charged one in the marginal seat of Coogee before the March election. The Labor opposition has pledged to build an entirely new school in the area if it wins government.