The six classroom and headteacher unions' end-of-year returns claim a combined membership of 962,000, a substantial increase on last year's 929,000.
The unions hope that this growth will give them greater political clout in their negotiations with government. The two biggest unions have agreed to consider national industrial action if Gordon Brown, the Prime Minister, insists on keeping their pay rises lower than the increase in their living costs.
Teacher numbers have increased over the past three years, partly because of Labour's investment in education.
In its end-of-year return to the Certification Office, the National Union of Teachers claims to have 368,066 members, an increase of 1.6 per cent on last year (361,987). The NASUWT reports 298,884 members, up 3.1 per cent on last year (289,930). ATL increased its membership by 1.9 per cent from 203,241 to 207,057, and the Professional Association of Teachers increased 6.8 per cent, from 33,645 to 35,945.
Membership of the Association of School and College Leaders has increased 3.4 per cent from 12,341 to 12,760, while the National Association of Head Teachers' membership has dropped 0.6 per cent, from 39,521 to 39,292.
The figures must be treated with caution: some members are retired or belong to more than one union. The total declared membership of the four classroom unions comes to nearly 910,000, far more than the 560,000 working teachers in England and Wales. The fee-paying membership of the four unions, as declared to the Certification Office, is 740,000, which includes some nursery nurses and support staff and a small number of members in Scotland and Northern Ireland.
The NUT will next week schedule a ballot of its members to set up a political fund so that it can directly lobby the political parties. Delegates at its Easter conference said this would allow the union to campaign against "racist" right-wing organisations such as the British National Party.
The NASUWT told the Certification Office that it had paid more than Pounds 104,000 to political parties, largely for the opportunity to campaign at party conferences. More than 10,000 of its members sought to opt out of contributing to the political fund last year.
The other unions do not have political funds.