Councils are predicting a fiery reception for Douglas Osler, senior chief inspector of schools, who chairs the committee, and other senior officials.
Mr Gavin declared: "I would be failing in my duty as a professional educator if I did not express the real concerns that underlie these proposals. There has to be the worry that we have got the 11-plus back again."
Moray's eight secondaries have virtually stopped 5-14 testing in English and mathematics because of the uncertainty created by the revised plans, Mr Gavin told councillors last week. There was "particular irony" that confusion caused by the Scottish Office itself had prompted heads to act, "thereby providing a context for compulsory introduction".
There were "high levels of uncertainty" about the regulations ministers might force through. Many secondaries had built testing into their school development plans for 1996-97 but subsequently withdrew. Progress had been "extremely slow" because of the organisation required to test within the normal secondary routine.
Mr Gavin accepts tests will produce useful comparative data between schools and councils but stresses that co-operation is paramount at a time when resources are stretched. Publication of test results and levels of attainment in every primary would place enormous pressure on parents, pupils and staff.
"This sort of pressure was a major contributory factor for the removal of formalised testing at the age of 11," he said.
Mr Gavin maintains that the Scottish Office is ditching the 5-14 tests used to confirm pupil attainment in favour of "benchmark" testing. "The secondary sector is now faced with two testing approaches and organisational pressures alone will push schools towards the benchmark model," he told councillors.
In the primary sector, teachers are avoiding testing in the autumn term, raising concerns about continuity and progression in the 5-14 curriculum. Moray is currently investigating whether this pattern is being repeated across the country. The council is concerned that testing is focused on the spring and summer terms and that teachers appear to ignore previous reports on levels attained by pupils.
Officials also believe class teachers delay testing until they get to know their pupils.
Staff, however, are to be encouraged to look on testing "as more of a continuous process with due attention to the period August to December". The move will be accompanied by a staff development initiative on the assessment of writing, a particular difficulty for teachers.