At 6:30 a.m. the phones start ringing.

The substitute teachers who say "yes" are off, not to the most glamorous job, but to one that has a built-in guarantee: The day will never be boring.

Substitutes for elementary and secondary-school levels are needed. The qualifications and the pay vary, but the jobs are there. If you are thinking of substituting, listen to legitimate tales -- both horrendous and humorous -- told by old hands at the game. Then ignore the stories until you try it for yourself.

As a subtitute teacher for 7 years in District of Columbia schools, I've had days that were fun and days that were frantic. I've continued because:

I enjoy the teaching I can do; I feel I'm filling a real need; there is no better way of knowing how things are inside a school, especially if your children are there; the hours are perfect for anyone with school-age children.

There also is flexibility. You can say no when a child is sick or there is something else you have to do. If you say no too often, however, the calls will stop coming. Unless a flu epidemic strikes.

If you decide to try a substitute-teaching career, you must quickly develop survival skills (basically the same, regardless of the level you teach). An experienced teacher will have his or her tricks, but if you are new you must begin somewhere.

Develop an "I-am-in-command" persona, regardless of how you actually feel. Children can sense, just as pets do, an air of indecision, a weakness in the game plan. Once that weakness is sniffed out, the children will take charge, no matter their age.

(Remember what happened to weak substitutes when you were in school?)

When you arrive at a school, especially an elementary one, there may be elaborate plans on the board, a written guide for the sub, textbooks laid out and marked with current work, extra dittos, directions for use of lavatory and library . . .

But don't count on it.

If the teacher had not prepared to be absent that day, you will most likely be handed a folder that contains:

1. A schedule of times for class activities, all changed since the list was made up.

2. Lists of students in reading and math groups which bear no relationship to the present groupings and lead to endless arguments such as "I don't read with that baby group anymore."

3. Dittos from the past two years that the teacher ran off and then decided weren't worth using. Blackboards will have been erased, so there is no way of telling where the children are in any subject area. Markers in the teacher's editions of textbooks are "out of place," according to half of the class.

So you are winging it.

This is not an overwhelming problem if you've been substituting for a while. You will have established during the at-home call the grade level you will teach. You'll arrive laden with all sorts of suitable workbooks, reading books, games and activities for that grade.

If you are new to the class and you discover there is no plan, you will despertately peruse the schedule and begin worrying about such matters as reading (what, how?) or math (what can they do?). Sometimes neighboring teachers will help.

But beware the novice's common tendency to ignore crucial issues that establish control.

Take an item on the elementary class schedule called "health needs," a euphemism for lavatory. This is typical of the many areas -- the opening of school, to give, or not give, passes -- where firm decisions must be made.

If you have a class that is accustomed to a timed, segmented schedule, you will find a number of self-proclaimed assistant teachers pouncing immediately if you developed one minute from the prescribed pattern. But if you ask the class the usual procedure, they know you don't know and you will be given 16 different ansers on "the way we do it."

The wise move is to ask an early arrival to give you a private synopsis of where they are in subject areas and how things are done. In the younger grades no one will be sure of the answers, but in the upper grades you should end up with some idea of usual procedures.

Beware if you have not discovered the classroom pattern. Suddenly a dozen or more students will announced "It's 10:30, time for health needs." This kind of situation will make or break you. An immediate decision is mandatory. k

One option: Take the entire class and line them up in the hall while they one-by-one use the facilities. It takes even the novices only 1 second to see the problems of keeping an entire class orderly when you cannot raise your voice and you don't know any names.

If you choose this way, every teacher on the corridor will come out to assist you in maintaining order.

"Class, I am shocked," they will say. "You never act this way when your teacher is here."

This does not help your confidence.

Another means of taking care of health needs: Send two (of the same sex) at a time. This keeps the rest of the children contained in the classroom. But what happens if the two do not return?

One of the prime rules of any school is that a class, for safety reasons, may not be left unattended. How do you get the escapees back?

You can try sending others after them, ignore them, or send to the office for assistance. Prayer sometimes helps.

Another option: Ignore that item on the schedule and go on to something easier to deal with. But if the children, are too young to tell time, they are certain to need that trip to the lavatory. Skipping it will bring bigger problems later on. If the children are old enough to tell time, there's no way you're going to slip anything by them.

The rule of thumb on this and other problems of class management: Make your decision early and stick to it. There may be no right way, but you as a substitute must act as though the way you have chosen is the only way. In several school systems the schools themselves call for substitutes. You sign up for schools near you, where you feel comfortable. In districts where there is a central calling system it is still a good idea to visit the schools first.

Classes almost always will be under control when the regular teachers are there. But anticipate what you might run into; check out the behavior of students in the halls, lunchrooms and stairways. You can often predict trouble for substitutes if the students have an "anything-goes" attitude outside the classrooms. This means school rules are not consistency enforced by the administration. When a teacher is away, the students will play, or do worse.

If you decide to substitute you are sure to have times when you feel as though you are walking on your knees at the end of a "teaching" day. But there will be times when you leave with a sense of accomplishment, when you say, "We all learned something today."

That can make it all worth while.