A POPULAR THEME among journalists today is that the quality of public education has diminished miserably. Using a "proof in the pudding" argument, they talk of our lowered national averages on scholastic aptitude tests, of high school graduates who cannot write, and of college students who cannot think. The blame for this devastation is often laid at the feet of the teacher.

But if teachers are not properly educating the students, why not? Are teachers today not as bright as those of years past? Are they poorly trained? Is the job so taxing today that only a genius could do it right? Are the financial rewards so lacking that our industrious young have sought careers elsewhere? Or are teachers hampered by other problems within the system that make teaching more difficult than it was years ago?

What, then, is the proper way to educate or train a teacher. As a graduate fellow in education years ago, I took many education courses. Not one helped me become a better teacher.

Primarily I learned to teach by observing other teachers, by discussing problems and exchanging ideas with them, and by experimenting with different solutions. A mountain of education courses would not have helped me if they did not require me either to teach or to observe other public school teachers, and they didn't.

The one course I can think of that would be helpful, at least to English teachers, is one I have never seen in a college catalogue. It is a course on how to teach writing. It is silly to assume that a college student who excels in literature courses and who can write proficiently will necessarily know how to teach writing.

But are poorly trained teachers really the chief problem in our schools? Or is the nature of the teaching job such that almost no one could be truly excellent at it?

Consider the English teacher. He faces an average of 150 students a day. Five times a day he leads 50-minute discussions, with those five classes often involving three preparations. In the six minutes between classes he confers with individual students. If he is also a dedicated writing teacher, he will assign compositions once a week. Imagine taking home a stack of 150 themes to evaluate!

While it is true that schools often relieve English teachers by assigning composition graders, problems develop when one person is teaching writing and another is evaluating the papers. Futhermore, if the English teacher is not trained in a systematic method of teaching and evaluating writing, the composition grader certainly is not.

Can anyone who has not taught fathom the amount of energy that goes into such a day? And if teacher has to contend with discipline problems -- angry students in a fight, the ones on drugs who can't control their giggling -- the complexities of classroom management increase. Sometimes I think it's a miracle that there are effective teachers.

Who is the person who chooses teaching as a career? Is education failing to attract the best and the brightest? There was a time when intelligent, college-educated women selected a career in teaching because it seemed a respectable occupation to pursue while one was waiting to raise a family. Today the picture is different. Economic necessity, women's liberation and expanding opportunities have caused women in particular to take a fresh look at careers and to select one based on long-range, not short-range, goals. For the hours and energy a competent teacher puts into his day, he would be better paid in another line of work. Several teachers I know have left the field for that reason alone.

A mediocre salary might be compensated by the satisfactions derived from teaching. Teaching is exciting and stimulating, and the appreciation of one's students is a great reward. Consider, however, the hassles. Teenagers are often rebellious. Many do not respect authority, preferring instead to antagonize authority figures. The news media are filled with stories of student violence.

The satisfaction of teaching must be weighed against the trials. It does not surprise me that from time to time a very good teacher will leave the profession. I wonder how many potentially good teachers eliminate teaching as a career choice.

Finally, there are a host of logistical problems that a teacher must contend with. I have taught in classes where there were not enough books. There used to be an adequate supply, but students lost them, and the shelves could not be restocked until the next fiscal year. Moveable desks add distractions that were not present in older classrooms. Frequent interruptions from the attendance office, sometimes as many as five in a class period, can disturb the flow of a discussion or student presentation.

The learning that takes place in a classroom is influenced by the total environment. If students like school, if they view it as a social and educational haven, then their enthusiasm will spill over into the classroom and they will learn from each other and from their teacher. If, on the other hand, students view school as a repressive place that they must endure, if they are pouring their energies into after-school jobs and giving only minimal attention to studies, it will be more difficult for the most inspiring teacher to reach them.

The attitudes of the students, the parents and the administration all affect what transpires in an individual teacher's classroom. Certainly, the quality of teaching is a crucial factor in determining the academic success of our students, but we would be remiss to overlook any of the several factors that influence the quality of education today.