Only 6,762 headteachers had agreed performance targets with their governors by December 11 2000, Estelle Morris has said.
The targets, which will cover areas such as finances and classroom performance, are designed to clarify the relationship between headteachers and governing bodies and to promote improvement.
The Gvernment estimated that a further 2,076 were set to do so by December 31 2000, the original deadline. But this is just 42 per cent of heads in state schools.
Ms Morris, replying to a question from Tory MP Graham Brady, said that the deadline had been extended until April 6 of this year "to provide flexibility".