Exotic, I think it's one of those things that varies with demographics! We take between 35 and 40 children swimming once a week for half a year, and the 'non swimmers' group is ALWAYS the largest of the three groups.
A couple of points reinforcing what others have said:
-It's voluntary. Don't pay it if you don't want to, but then don't complain if the school doesn't invest in new reading books or whatever. As it's a NC subject, the school has to cover the cost regardless. Essentially, the per capita money in the school budget for 'swimming' may stretch to pool hire and (for bigger schools where larger numbers of children go swimming) teachers ... but the biggest cost is coach transport, which is non-optional in many areas such as rural ones. If that cost comes out of the school budget, there is less for other things....
- Those who don't pay will still have swimming lessons. The clue is in the 'voluntary contribution' - no child will be prevented from taking part in an activity just because their parents haven't paid it.
- It's a national curriculum subject. You don't get to opt your child out of music in school because they have music lessons out of school, nor maths because your child does Kumon, or football because your child plays for the local professional club's youth team. Swimming is just the same.
- All teachers and TAs taking swimming lessons have had training, it's not just something we 'turn up and do'.
- We never leave children behind in other classes - the class staff either go swimming or have non-contact time, and it is disruptive to the other classes (different age group from those who go swimming) and of no benefit whatever to the child left behind. All children from the year groups who go swimming come with us, any who e.g have no swimming kit have to sit on the side and watch, under the supervision of the very scary lovely ex-policewoman who volunteers to help supervise the children on the bus.
So, at least where I teach, if you chose not to pay, your child would still have to come to the pool, and would still be given lessons as long as they brought their swimming kit...BUT the pleas for help with fundraising might get a little more plaintive and the investment in resources and visitors and books will get less... it's a choice that you make.
(Also, on a more emotive note, we have a LOT of non swimmers from very disadvantaged backgrounds. If those who could contribute don't, then ultimately it may be that schools have to decide, NC subject or not, that they can no longer offer swimming or do so at such a low level that no non-swimmers ever learn to swim. And whose fault would it be when one of those children drowns?)