The principals and their deputies were supposed to sign the agreements this year. The performance of school heads is to be measured against the academic performance of schools and be linked to performance in the Annual National Assessments and National Senior Certificate exams.

The contracts are aimed at increasing the accountability of principals. But the appraisals have not been completed or welcomed by teacher unions.

A principal at a Limpopo primary school said: "We've never seen the performance agreements. We have just been told we have to sign them. What is scary is that people might lose their jobs because these might be used to settle vendettas."

The Western Cape was supposed to be one of the first provinces to implement the appraisals but this has been delayed by teacher unions.

Western Cape education spokeswoman Bronagh Casey said: "We are busy with final negotiations with the unions. We hope to start implementing them in the next few months."