We still await a considered assessment of the way a professional institute, committed by its Royal Charter as much to the advancement of learning as to its members' own interests, was transformed into one of the most effective trade unions, one which was to resist better than almost any other, and certainly better than its teacher counterparts south of the border, the best efforts of the Thatcher government to emasculate it.
The key period of development came in the 1970s. There were pointers to a bracing new climate - joining the Scottish Trades Union Congress in 1971 and the TUC itself in 1977, the arrival as general secretary of John Pollock, already a national figure who had been chairman of the Labour party in Scotland as well as an outspoken headteacher. But it would be simplistic to designate these as explanations of change.
For a start there was no overnight conversion to militancy. The teacher shortage of the sixties had allowed the profession to flex its muscles as well as giving cause for anger as members struggled with overcrowded classes, part-time education and a curriculum that ill served a substantial part of the pupil population. Glasgow in the sixties saw the first teacher strike and so the action which accompanied the pay demands of the seventies - resulting in the Houghton and Clegg inquiries - was not entirely novel.
But the national scale of disruption, the aggressively effective leadership of Pollock and the bitterness felt by Secretary of State Willie Ross and the Labour government did signal a new era. White-collar unions everywhere were taking the lead as the old manual unions struggled against declining industries. The student agitation, which hit continental Europe in 1968 and Scotland rather later, bred a generation of young teachers eager to fight for school reforms and better conditions of service. Especially in Glasgow and Edinburgh local EIS associations recruited young activists on a scale not seen before or, it has to be said, since.
Much was gained - a contract limiting teachers' hours and commitments, maximum class sizes of a kind still only being talked about south of the border by Tony Blair's Government But there were losses, too. Teaching, which had been regarded as a respectable if unglamorous and ill rewarded profession, became embroiled in controversies, its members tarred with the excesses of a few, mainly south of the border. Victories in pay campaigns were never total, and gains appeared to dissipate quickly. So there were signs of increasing militancy and, amid bitterness, the EIS leadership had to beat off repeated challenges from the left.
Yet the fundamental strength of the EIS within the profession, where it came to represent four-fifths of all teachers, and among the general public was demonstrated in the long dispute at the height of the Thatcher ascendancy when the miners were being taken on and beaten. The EIS was well enough organised and funded to win concessions after two years' struggle. Despite repeated disruptions to schools and threats to the SCE exams, parental support for the teachers' case was barely dented. The strategy of concentrating on schools in Conservative seats, still then a significant number, was innovative and did not cost too much. With impudent panache Highland schools were targeted to mark the centenary of the 1886 Crofters Act.
But the institute could not avoid the restrictions of trade union legislation. By the late eighties the era of national disruption was over. Direct pay bargaining survived in Scotland when abolished south of the border, but the scope for wresting above-the-odds settlements from employers largely disappeared. Conditions of service applicable in the seventies were painted by the local authorities as costly and obsolete. Teacher unions were put on the defensive.
The institute's response was to accept a changed role. Devolved management was coming to schools, 32 authorities were born out of 12 predecessors. So the EIS remitted much of its activity to its local associations. Members in further education colleges faced a particular challenge as money-conscious business managers took over from regional councils.
Included in the new strategy was a re-emphasis of the institute's educational role. Scottish schools and colleges could be protected from the ravages of a Conservative government only if teachers were regarded and rewarded as skilled professionals. Again, it is simplistic to link changes of direction to changes of leader. But neither of John Pollock's successors, Jim Martin and now Ronnie Smith, has revelled in industrial action. Other times, other ways. The strongest vote of confidence in the EIS and other teacher unions came early last year when 40,000 parents and teachers marched against the cuts in education. The Government was rattled and strove throughout the rest of its life to demonstrate good intentions, albeit without the money to back them and therefore unsuccessfully.
The political challenges for the EIS now are two: matching the aspirations of teachers to those of a more sympathetic Government committed to education but still loath to spend money, and defining for the first time in 150 years a relationship with a legislature just along the road.