Maybe people won't agree with this, but I think council pools need to do less weekend lessons and more swim sessions. At my local pool there are literally 10 hours over the whole weekend across both pools that are family swimming sessions. The rest of the time it is lessons. Bearing in mind that children will most probably be awake for about 10-12 hours each day - that's painfully little!
Also that 10 hours is sometimes both pools open but sometimes just one, so if you are a little person who needs warmer shallower water, or a bigger non-swimming child who can't really swim in the shallow pool, you won't have all 10 hours open to you. I know for a fact that you HAVE to arrive 15 minutes early for weekend family sessions, otherwise both pools with be full.
In terms of money,, lessons at our local pool have to be booked in termly blocks and fully paid for at the time of booking. Swimming lessons are £31 a month for one lesson a week, kids session are £3 or free if they are under 3.
I am not knocking swimming lessons in any way, I have no doubt they are brilliant for a lot of children, but if the main option for actually learning to swim requires people to commit to the same time every weekend and have £31 per child avalible at the start of each month, instead of being flexible during the weekend, not required an every weekend commitment, and only requiring maybe £13 to be avalible at once - it's not surprising kids can't swim.
I absolutely see the benefit of proper swimming lessons, and am in no way claiming they aren't amazing for the children that have them, we can't be surprised that the number of children who can swim is small, when the chance to learn to swim