Kim Merchant dreads September and the inevitable battle over the timetable.
The 29-year-old maths teacher works part-time at an independent school in the Midlands. Currently, she has Monday and Thursday afternoons off. But she says her school would prefer to sandwich her "part-time-ness" in the middle of the day.
"What good would that be?" she asks. "I wouldn't be able to go home. I couldn't pick my son up from school. All I could do is hang around the town."
So she fights to get her lessons and her non-contact time when she wants them. "No one consults me about the timetable and yet I teach 32 out of 40 lessons."
When Kim stays an unpaid-for afternoon to attend a parents' evening, she keeps a low profile. "Otherwise they'll be asking me to cover for classes.
I couldn't ask them to pay for the extra afternoon. They would never agree."
Kim's relationship with her head has been soured by wrangles over part-time issues that could have been sorted out when she started six years ago. In the autumn, they clashed over staff meetings currently held after school on Thursday when Kim is not there. She refused to stay, unpaid, at the school, or to drive back in the evening, a 40-mile round trip for which she would get no expenses.
"The head said she expected attendance at staff meetings to take precedence over my part-time-ness. Well, I don't agree. But nothing has been resolved."
Another issue is responsibility points. Kim has one for organising the school's exam timetable every year. "I do the whole job. Yet I only get 75 per cent of the money. Is that fair?"
The worst thing is not knowing where she stands. "In three weeks' time my head of department goes on a term's secondment abroad. I may have to take over her form responsibility. But no one has told me. And no one has thought about the fact that I don't get paid to arrive at work before 10.30 on Friday. What happens to my form then?"
Kim is prepared to fight her corner. She has joined a union, but says that they only tell her that it is all a "grey area". Mostly she takes the advice of a close friend who has been part-time for years.
"Only rock the boat if it is absolutely necessary," she says. "Otherwise, just do what they say. It is not worth the hassle."