Under the old scheme of Government bursaries, trainee teachers in shortage subjects such as science got a special flat-rate payment, whether they took up jobs in teaching or not.
But now the rules have changed and education departments at universities such as Newcastle, Portsmouth and York have found themselves free to reward what they regard as talent and loyalty.
This year's training courses have, on a national basis, been 20 per cent short of science students and 33 per cent short of maths trainees. Student teachers of modern languages and religious education are also eligible for the additional money, which comes through the Teacher Training Agency's priority subject recruitment scheme.
This was introduced in 1996 to replace the system of flat-rate bursaries, which were felt to have only a short term effect. Under the new regime, universities are asked to devise their own system for rewarding trainees in shortage subjects.
At Newcastle University, for example, they are entitled to as much as Pounds 2,000, but only if they meet certain conditions.
Students of maths and science receive one third of the money when they pass an initial "diagnostic" test; one third when they pass their exams; and the final third only when they have got a teaching job.
Newcastle is also keen to improve the quality of its maths and science recruits. A large portion of the available money, Pounds 1,500, is restricted to those with first class or upper second class degrees. Trainees in popular subjects like English have, in the past, tended to be better qualified.
Newcastle has around 30 out of 200 postgraduate trainees receiving the full Pounds 2,000 award. It is also offering an additional Pounds 500 to students with dependent children.
The University of Portsmouth is convinced that money is an important incentive. Its maths, science and foreign language students receive Pounds 450 and then a further Pounds 250 if they obtain a teaching post. There is also hardship money, travel money and help with industrial placements available for shortage students.