A third of all graduate school teachers drop out of teaching within five years, according to official figures.
Higher and further education minister Baroness Blackstone revealed that out of the 10,670 teachers entering the profession after qualifying in 1993, only 6,990 were still teaching by 1998.
The figures, produced by the minister in response to a question by Baroness Blatch, Conservative education spokeswoman in the Lords, showed that maths teachers were among the most likely to have quit the profession with 38 per cent having left by 1998.