Beware of exploitation
You have written about the problems of declining pupil numbers. Will this make it harder to find part-time teaching jobs?
It is hard to be specific about what will happen to part-time posts in the future. Falling rolls could lead to some schools axing part-time work in favour of full-time teachers. On the other hand, some schools might find that they can no longer afford a full-time teacher but have enough money for a fractional appointment. What matters more is what you can offer the school, and how flexible you can be. If you only want to work Tuesday to Thursday and are never willing to help out on other days in a crisis, you will be less welcome than someone who can fit in with the needs of the school. But don't become exploited. It is too easy for part-time work to take up the whole week so that you become, in effect, a full-timer on a part-time salary, getting the worst of both worlds.