Pauline Colangelo, who has been teaching in Trenton, N.J., schools for longer than she likes to admit, says she is "more than a little bit tired of taking the blame for everything."

Society demands that we do everything," she said today. "It wants school to meet all the needs that the family, the church and the community used to provide. Yet it doesn't want to give us the freedom to use our expertise to get things done."

Colangelo has stayed with teaching through some of her school system's roughest days. But, according to a study released today by the National Education Association, many experienced teachers like her have not, and are leaving the classroom in record numbers.

The number of teachers with 20 years' or more experience has dropped in half since 1961, with most of the decline coming in the last five years, the study found. It has left the nation's schools with the youngest faculties in at least 15 years.

Moreover, NEA found teachers more dissatisfied with their jobs than at any time since the nation's largest teacher organization began making similar surveys in 1961.

The NEA study found that only six teachers in 10 plan to teach until they retire, and 10 per cent of them are simply teaching until they can find a better job. Even more striking was a discovery that 37.5 per cent of today's teachers aren't sure if they'd teach if they had to start their careers over. The number was particularly large in large Northeastern school districts, where 29 per cent of teachers surveyed said they were certain that they would not teach if given the choice again. This compared with just 10 per cent of those questioned 10 years ago in a similar survey.

The job dissatisfaction comes at a time when the nation's 2.2 million teachers are better paid, better educated and work under better conditions than ever before, NEA said.

The typical teacher, the study found, earns $12,005 for teaching 180 days a year, works in a classroom with 25 students, is 33 yeas old and holds a bachelor's degree. Seventy-one per cent own their own homes, and 37 per cent hold master's degrees. Fifty-two per cent own two cars, compared with 35 per cent 10 years ago.

The study, however, offered only vague clues as to what is bothering teachers. It said, for instance, that 17 per cent of them have negative feelings about students' attitudes and discipline, another 17 per cent feel they work for incompetent administrators, and 14 per cent feel overworked. The big change in attitudes appears to be in student discipline and the negative way in which teachers feel the public regards them.

A deep undercurrent of frustration is easy to sense among the 7,750 delegates to the NEA's annual four-day convention here, which opened today. It is reflected more in conversations with teachers than any official pronouncements.

"The people I know who've quit in the last couple years seem to be happy to leave," said Claude H. Sasse, a social studies teacher from Hagerstown, Md. "They talk about discipline delcining - parential discipline more than school discipline. Also there's interference coming from all quarters. Someone, who might not know anything about education, has a bright idea. So we try it. So now we're into sex education, we feed kids free breakfast, we have cops in the hall-ways, and we're doing all kinds of other things.

"Every time a problem comes up, we run scared," he added.

Teachers interviewed blamed many of their problems on the parent of the children they teach, and what they expect of them. "All of the problems of the world seem to land on the steps of the schools," complained Isabelle Hickman, a New Jersey business teacher. "What I'd like to see is a revival of pupil interest."

"We're supposed to be sociologists, we're supposed to be psychiatrists, we're supposed to be babysitters. We're supposed to be the parents," said Patsy Haynes of Sacramento, Calif. "But when you call out to the community for help, the parents always turn back and say that's the school's problem, or I'd like to help you but I'm too busy."