Teaching must stay an all-graduate profession despite an impending recruitment crisis, Matthew MacIver, registrar of the General Teaching Council for Scotland, told heads.
Scotland was the envy of many countries for its professionalism but that was now at risk. "Don't be in any doubt, there are some people who would want that wall to fall down," Mr MacIver declared.
Some people thought that anyone with skills in a particular area could teach, an apparent reference to the new emphasis on vocational education in schools. "I believe quite passionately that we cannot compromise," he said.
Mr MacIver also said it was a fundamental mistake to remove the need for registered teachers in the pre-school sector, a battle the GTC lost.
Future demands for thousands of extra teachers to work, for example, in the transition years between primary and secondary should be met by retraining existing and fully qualified teachers.
He argued: "It's not parachuting people to teach whatever they are going to teach without registration and qualifications. We in the profession have to adapt and change but there are some things that I believe are fundamental and you can have flexibility without compromising standards.
"I worry when people talk quite glibly about the 10-14 report and people say these teachers in secondary school are rubbish. I do not believe there are hundreds of primary teachers in Scotland who are just desperate to go into S1 and S2 in secondary school to start teaching maths and English.
They are not there.
"We need to look at it professionally and not in terms of a quick political fix."
A case in point was a biology teacher who after 30 years asked to change to music. He was a skilled musician who played semi-professionally. That was the type of flexibility he favoured.
Mr MacIver accepted there were some pupils whose needs were not being met but an age breakdown from the chartered teacher programme proved that teachers in their 40s and 50s were not switching off and were keen to develop professionally.
* Central Belt domination of teacher training is preventing many mature students entering the profession, Mr MacIver said. Only 15 per cent of schools receive a student on placement.