The government has given teachers' unions a "take it or leave it" message as it attempts to reform staff contracts in schools.

David Miliband, the minister for school standards, has told union leaders that they must agree to changes in working conditions by January 15.

However the National Union of Teachers is continuing to resist part of the reforms, which would see classroom assistants taking lessons in place of qualified teachers in some circumstances.

The NUT has described the idea as like asking "the theatre sister to take over the brain surgery".