His pound;72,000-a-year post was advertised this week. The successor will work in tandem with Mr de Gruchy from next Easter.
Mr de Gruchy told The TES that he had always envisaged a stint of around 10 years. Immi- nent restructuring of the union, to be led by his successor, also made it the right time to leave.
He added: "This last decade, like the I 980s, has been one of non-stop turbulence in the profes- sion. I have been proud to have been part of a team ... who have succeeded in increasing the influ- ence of the NASUWT."
During Mr de Gruchys time, the union's membership has swelled from 120,000 to 190,000.
Probably his proudest moment came in 1993, when the union won a High Court victory over the 'Londn borough of Wandsworth over its decision to boycott national tests, on the grounds of workload. This forced the Govern- ment to be much more concilia- tory about the tests.
He will continue to work for the union for a year after standing down, representing it on the Trades Union Congress and on international committees includ- ing the global teachers' body, Edu- cation International.
He plans to write a history of the NASUW[.
His deputy, Eamonn OKane, is the front-runner to succeed him. Mr de Gruchy was himself deputy general secretary for eight years before rising to his current position.
Chris Keates, assistant secre- tary for policy, and Mick Carney, honorary treasurer, have put their names forward. Assistant general secretary Jerry Bartlett is another contender. Shortlisted candidates will be interviewed in February by the national execu- tive - though any member is free to stand against them in a ballot.
Former president Sue Rogers denied she would be standing.