Fellow teachers - if they don't take you for the new caretaker - can be very supportive. It is not uncommon to be heartened with the words: "The last supply teacher we had left in tears, vowing never to teach here again."
Here is a checklist based on one year's experience in West Yorkshire schools: * The early morning phone call will not make you happy It is of immense value to be rung up the previous night. That way you can prepare lessons. Better still, you can have a word with the teacher who will be absent. But life is seldom like that. It's far more likely that the head will ring you up at 8:15am to tell you that you can teach anything you like because the regular teacher took all the maths and English books home to mark.
* Don't get hung up on gender
If the regular class teacher is a woman, then no matter how butch you look or act, you will still be called "Miss".
* Assert your authority right from the start
In most schools monitors bring round the registers. This means that you have only a few seconds to read through the names.
At my first school, more than 90 per cent of the children were Asian. The Zakias, Howabibis and Afzals were quick to tell me that I had put the emphasis on the wrong syllable. It was only after I had mispronounced 35 names that I learned that they didn't usually do it that way. They all had numbers to call out.
* Always have a seating plan
As soon as children learn that a supply teacher is coming they in-variably decide to sit next to their friends. Should you be forewarned that little Johnny, who sits at the back, can be silly, you can get caught out by telling little Johnny off - only to find that he is actually sitting under your nose and you have chastised the class goody-goody, thus alienating the only ally you could have relied on.
* Remember that every school operates a different system
"The children are colour coded for maths," is a way of telling you that they are streamed. After visiting a few schools I thought I had cracked the code. Red group was always the smartest, blue stood for bright, green meant good and yellows were, well, yuckie.
For efficiency's sake I had a sheaf of worksheets already colour coded in readiness. However, it didn't last long. Some teachers made their best group yellow and the slowest yes, of course, red.
* Being a nurse is part of the job description
If there is a note in the register warning you that a pupil might have an illness, then they will have it when you are in the classroom. Little asthma attacks are manageable. So are tablets to be taken at playtime - but diabetes is more serious.
Ahmed's eyes glazed over and he began to flop off his chair. Everyone in the class scrambled for his glucose bottle in the cupboard because they knew he often came to school without having had any breakfast.
Jonathan's friends stepped back rather than forward. He came to tell me that his tummy felt funny . . . and then was sick all over the desk. That was after I had been in the classroom for all of three minutes.
* Don't expect any administrative favours
Supply teachers standing in for just one day will invariably find that it is their turn for playground duty. At one school, with lots of Muslim children, the boygirl divide was so acute that boys would not line up with girls. Even when the boys lined up at the back no boy would be first because by definition he was behind the last girl.
That was in the playground. You can imagine what a commotion there was when it came to getting changed for PE.
* Be wary of television programmes
"We always have TV on Thursdays," may sound tempting but every video unlocks differently, operates differently and has different remote controls. Even if you get past that stage, half the class will tell you they have seen a particular programme and the other half will tell you they have not. Most will tell you that they normally watch two 20-minute recordings at a time.
The funny thing is, very few of them confess to doing follow-up work, especially after spelling programmes.
David Norris has been a supply teacher working with junior school children in the Batley, Dewsbury and Huddersfield areas of Kirklees