More than two out of three primary deputy heads are women, yet the same proportion is not reflected in applications. And the same problem is apparent when comparing the number of applicants from primary schools with those from secondaries.
That the NPQH will soon be made mandatory for all new heads - perhaps as soon as the year 2000 - further highlights the need to make sure opport-unities for taking the first step towards headship are equal.
It may be that the system of selecting candidates is contributing to the imbalances. At present, candidates are self-selecting in the sense that anyone can apply to join the NPQH through the local assessment centre. This could militate against less confident teachers and those in smaller schools.
The funding system may also need looking at. All local authorities are given an amount of money through the GEST system - based on the number of schools in their area - to pay for NPQH training. Some authorities, the TTA suspects, have underspent and will need to encourage more candidates. But for others the money has run out and candidates have been declared "eligible" - they have met all the requirements for starting the course - but failed to gain funding. So far 66 candidates have been forced either to seek funding elsewhere or pay their own way.
This year the Government has put Pounds 4.5 million into the NPQH, which should cover the estimated 4,000 candidates. But if imbalances are to be eradicated, it may be that a more rigorous and consistent system of selecting and funding candidates is needed.
A potential problem for many candidates, which may hit women with families especially hard, is that the NPQH involves a heavy commitment of time outside working hours. The structures of the courses vary, but often involve weekends and evenings. And while up to 20 per cent of the cost of supply cover for candidates is provided in the GEST allocation, the evidence suggests this may not be consistently available from one authority to another. This, again, could deter teachers in primary schools - usually more tightly staffed than secondaries because of their size - from applying.
Anne Evans, manager of the West Midlands NPQH training centre and a member of the TTA's management development group, says it is too early to jump to conclusions.
"The recruitment process was rigorous, and maybe some people were reticent about applying because they wanted to see what it would involve first," she says.
Angela Preston, deputy head of TP Riley community school in Walsall, a candidate in the NPQH trials who has advised teachers in her area who were considering applying, suggests that a course like the NPQH is much more accessible for secondary school teachers. She also raises the question of whether heads are supporting their staff fully.
"People in primary schools are more likely to be teaching full time so it's much more difficult to release them on a regular basis."
The National Association of Head Teachers takes an uncompromising view of this state of affairs and of the patchy provision of supply cover for NPQH students. "Anybody who is deemed eligible should have funding," says Esther Williams, the union's senior assistant secretary for training and development. "Unless the NPQH is resourced in an equitable way it will come down to whether an individual can afford to do it or not. It is an equal opportunities issue. "