Albert Shanker, savvy president of the once-militant and strike-prone American Federation of Teachers, startled even some of his supporters last month when he voiced support for giving students some choice in picking their public schools.

Later, Mary H. Futrell, president of the rival National Education Association, told The Washington Post that she wants her union to advocate instituting a national test for new teachers -- signaling what could be a dramatic reversal for the nation's oldest and largest teachers union.

Those recent statements by the presidents of the two largest teachers unions mark a conscious recognition by Shanker and Futrell that times are changing and that they are must try to persuade their reluctant followers that they too must change.

"There has been a watershed change in the attitude and priorities of the two teaching unions," said Scott Thomson, director of the National Association of Secondary School Principals.

"It's enlightened self-interest," he said. "They realize that for the benefit of their own members they have to focus more on the performance of teachers, improving the classroom situation and the quality of teaching. No longer is their first priority 'How can I get more benefits?' Their focus now is, 'How can I improve the quality of teaching?' "

The shift in public attitudes about education began with the report "A Nation At Risk," which warned of a "rising tide of mediocrity" in American education. That conclusion launched a massive national effort for educational changes.

While not abandoning their longtime agendas of collective bargaining and improved working conditions, the NEA and the AFT have started to adopt the popular lexicon of school reform: tougher teacher standards and a return to basic curricula.

The unions' shift also reflects the changing membership of the two groups, as well as the clientele they serve. As older teachers retire, they are often replaced by younger ones less committed to making teaching a lifelong career. Many new teachers also are more concerned about upgrading the status of the profession.

"Both organizations have to tailor their message to the new young professionals coming in," said Scott Widmeyer, AFT communications director. "People who are entering the profession, they may want to teach for six years and then do something else." Surveys, he said, find fewer teachers interested only in salary and working conditions.

"It's a whole generational change," Widmeyer said, "not only in the membership but in the population we have to serve. The kids coming into the school system are the kids of Yuppie parents who are highly educated and know exactly what they want for their kids."

Faced with those factors, the unions have started to shift.

The most obvious evidence of this change was Shanker's call, in late January, for a national examination for new teachers. More recently, in an April 27 speech to New York state teachers meeting at Niagara Falls, Shanker said teachers "must take a step beyond collective bargaining" if they want to improve their status.

"Collective bargaining has been a good mechanism, and we should continue to use it," Shanker said, "but now we must ask whether collective bargaining will get us where we want to go."

The NEA has been slower to move. Futrell told The Post: "We have not retreated . . . . We shall support the social issues. We shall support affirmative action. We shall support collective bargaining. But the times have dictated that we place more emphasis on the professional issues."

The NEA, for example, has agreed with school principals on a new book that will outline the responsibilities of princials and teachers -- the first such joint effort after years of confrontation and hostility.

The two unions' markedly different pace in responding to the public pressures reflects, in part, their different internal structures. At the NEA, Futrell with a limited term must rule by persuasion, and she must contend with an entrenched bureaucracy.

At the AFT, with its hierarchical structure, Shanker is free essentially to rule his union as a one-man show, announce policy shifts in news conferences and public speeches, and drag his followers along.

Denis Doyle, education policy analyst for the American Enterprise Institute, said: "The risk Shanker runs is getting so far in front of his membership that he leaves them perplexed."

Some say that fear may have been behind Shanker's unusual May 20 interview with United Press International, in which he sharply criticized Education Secretary William J. Bennett as a bungler not concerned about education.

The new emphasis on upgrading teaching -- and the speed with which the unions have pursued it -- also have provided an interesting reversal from the traditional roles of the two groups. The NEA, since 1857, has considered itself the "professional organization" for teachers, while the AFT, a member of the AFL-CIO, has been perceived as a feisty, sometimes militant, union.

"The AFT was always the scrappy, streetwise, bare-knuckles union," said Doyle, "and the NEA was the prim and prissy bunch of professionals who wouldn't dare think of themselves as union types. It's been a total transformation, a total role reversal."