"At that stage," she says, "I was still thinking of returning in four to six weeks. I didn't know I'd be having chemotherapy."
In the event she was away from school until the start of the following school year, eight months later. The complications of finding cover, and of lack of continuity for students, made an earlier return unfeasible. "Teaching isn't a job you can come in and do on the odd day," she says.
Researchers have found that pupils off school for extended periods are most affected by the loss of social contact. Pat Friday suffered the same fate. She heeded the hospital's advice to forget about her job for a while, but she found continued contact with colleagues and pupils vital for keeping her spirits up. "I cannot praise my head highly enough. He kept in touch, and came to visit. But he never talked about school work."
Pupils also gave lots of support. "They visited, and sent letters and flowers. Once, I had a friend here when the doorbell rang and she found a pupil from the boys' school standing there with a bunch of flowers."
Having breast cancer in a girls' school struck a chord with the pupils. Doctors suggested she talk to them about it. "The medical team's worst enemy, they said, was fear." So a few weeks after her return, she took an assembly for all 500 girls, together with a lab assistant who also had breast cancer.
"I told them some of the humorous episodes - and there are plenty," she says. For example, she chose to describe the comically prosaic business of choosing a prosthesis. "It was like being in a shoe shop, with my husband saying he preferred number three."
Pat Friday never once doubted she would return to her job, which she did,six weeks after finishing chemotherapy. "The most difficult part was the exhaustion. You forget the pace of working life. The school gave me a reduced timetable, otherwise I couldn't have coped."
There were some unexpected snags, too. "I tended to forget I hadn't taken a class through a particular course, and that I couldn't make the same assumptions about what they had covered. It was a bit like going to a new job."
On the other side of the coin, though, was the satisfaction of knowing she was back. "It was a great lift - a reassurance." And the support of pupils was a great help. "They were welcoming, and brilliant at carrying my books, for instance." Year 9 pupils even asked her where she had been treated so they could make it their charity for the year.
A year on, she says she has changed in several ways. "I can't be bothered with trivia now. I'm just as concerned for the girls and their progress, but I don't lose sleep if paperwork is a day late."
The acid test, she says, will come when the school has an inspection. "If I can be laid-back about that, I'll know six months of chemo will have been worth it."
Pat Friday's experience strikes a chord with Shona Walton, who, as Warwickshire's English inspector, knows the teacher well. In January 1994 she was involved in a serious car accident that left her with a badly fractured pelvis, among other injuries. She was in hospital for a month, then off work for a further two. On her return she was on crutches for another two months.
She, too, learned the importance of the support of colleagues and friends. "I had a visitors' book in hospital," she says, "with 200 entries.It's a humbling experience to know you are loved, and it's so important in helping you get better. Anyone who's thinking of visiting someone should just do it, even if it's difficult or inconvenient."
She has firm views about the management of the return to work. "You have to negotiate in an objective and open way what you can and want to do."
A reasonable employer, she says, will sit down and discuss this. "On the one hand they'll say that because you've been ill, they'll ensure you aren't given unreasonable tasks. On the other they'll say they do want everything you can offer - that you have professional skills and they want you to use them. "
In her case, for example, although she was unable to drive and agreed to arrange all her travelling to schools and meetings herself (directing her mileage allowance in appropriate directions), she did expect to work as an inspector.
"Within two weeks I was leading a full inspection, on crutches with a back pack. It was important that I was being valued as a contributing colleague. "
The framework for the person who is returning, she says, "has to be clear, explicit and time-limited, so you don't feel, for example, that anyone can say you are not pulling your weight."
Shona Walton shares with Pat Friday the subtle change in the approach to life that comes with living through a traumatic experience. "Every day, I think how I value my family, friends and colleagues," she says. There are physical differences, too. "I swim every week, because I hurt if I don't. I try to walk and cycle once a week. It makes you want to look after your frame a bit. "
Pat Friday was helped during her recovery by telephone support from the charity CancerBACUP. Its services include an advice helpline staffed by cancer nurses. CancerBACUP, Bath Place, Rivington Street, London EC2A 3DR. Tel: 0800 181199. www.cancerbacup.org.uk WHAT HAPPENS WHEN YOU'RE SICK
* A teacher with four years' service or more is entitled to 100 working days sick leave on full pay and 100 on half pay. (After only one year you'll have 25 days, increasing year by year).
* During your illness your employer can ask you to see a doctor to confirm you need to be on sick leave. And if you want to come back, the employer can insist you see a doctor first.
* If you take ill-health retirement, you can't come back to teaching or you'll lose your pension, even if you come back for a trial period.
* Inevitably, if you are heading for ill-health retirement, you will be on sick leave for a long time. But if you then fail to get ill-health retirement, the same evidence of your ill health may be used to sack you.
* You can't assume the right to come back to a less onerous job. (Many employers, of course, come to a satisfactory arrangement with the returning teacher.) * A good employer will work out a programme for your return - perhaps a less onerous timetable in the first instance, or an agreement that you can start later in the morning.
* Before returning to a lower-paid position, consider the effect on your pension. Teachers' pensions are based on the best year's salary in the final three years' teaching. If you voluntarily reduce that salary, you reduce your pension. It's possible to minimise this problem by splitting the pension so it's based partly on your higher earning years and partly on your final years. Take advice from your employer, union and the Teachers' Pensions Agency.