This translated into more than 4,000 teacher deaths from Aids last year - a third of whom were aged between 25 and 34.
The shock survey also found that teachers were leaving the profession in droves and more than half had considered quitting. HIV-related illness also fuelled high absenteeism and low morale.
Over and above those who died of Aids last year, 45,000 teachers were HIV positive - 13 per cent of the teaching workforce. Some 10,000 teachers (22 per cent of those who are HIV-infected) need immediate antiretroviral therapy.
ELRC general secretary Dhaya Govender warned that if South Africa failed to curtail HIV-Aids among teachers, the consequences would add "immeasurably and unnecessarily to poverty and social stagnation" in the country in the coming decades.
The survey, Study of demand and supply of educators in South African public schools, was commissioned by the ELRC following "worrying anecdotal reports" that teachers were leaving the profession in large numbers.
The survey was conducted over 18 months at 1,714 of South Africa's 26,700 schools. It reached 21,358 of the 368,548 teachers in public schools in 2003-4. Almost all teachers approached agreed to participate, and four in five provided specimens for HIV testing.
The survey also revealed that 55 per cent of teachers had considered quitting over poor pay or conditions, workload, lack of career development or recognition, job insecurity and lack of choice over where they wanted to work.