The letter was initiated by 200 teachers calling themselves Avon Heads Against League Tables. They are campaigning against the Government's "dogmatic app-roach" to national tests and league tables for 11-year-olds and "the infliction of GCSE-type bureaucracy" on the nation's youngest children.
The heads are strongly in favour of high-quality, fully-moderated teacher assessment. Their letter states: "In the context of the developing professional expertise of teachers in making assessments, and the supporting systems of moderation, we cannot see the justification for external national tests in 1995 and future years.
"Our antipathy to external testing is not solely a workload issue, but is based on educational experience, and our deepest philosophical and professional conviction."
Signatories to the letter campaign include Sue Barker and Tony McKee, secretary and chair of the National Primary Headteachers Association, which intends to hold its inaugural meeting at the University of Warwick on March 3.
This new association has been set up to campaign on five key primary school issues funding, monitoring and support time, special needs, the early years and inspection.
The other signatories are heads in Brighton, Cambridgeshire, Devon, Croydon, Gloucestershire, Liverpool, London, Oxfordshire, Staffordshire, Stockport, Sutton Coldfield and the Isle of Wight.
In the letter, the heads say teacher assessment is the most important component of the assessment process.
Despite the slimming down of the national tests this year, teachers know "they are still a waste of valuable time and do not give either teachers or parents any new or further information about the child's progress", the heads say.
They are also unhappy about the diversion of funds from key stage 1 teacher assessment to supply teachers and the lack of financial provision for key stage 2 teacher assessment. This cost Pounds 30 million on top of Pounds 469 million for changes to the national curriculum and Pounds 30 million on the 1994 aborted national tests - a "terrible" waste of money, the heads say.
If it had been spent on school buildings and equipment, standards would have been raised with or without the national curriculum or testing, they say.
They are also concerned about the bureaucratic new arrangements for assessment level 4 at key stage 1. "To expect a six-and-a-half to seven-year-old child to take a key stage 2 external test in order to achieve level 4 is assuming that the child also has covered and understands the key stage 2 curriculum. This is ludicrous.
"It would be far better to provide an appropriate and extended key stage 1 curriculum.
"What we urgently need now, therefore, is government and public recognition of the quality and status of teacher assessment, and the facts that effectively moderated ongoing performance-based teacher assessment is the best most effective and most efficient way of assessing our children; and then an opportunity to be involved in and consulted about the best way to put this into effect."