I think it depends on the pool's showers and changing facilities, tbh. For years my DS went to lessons in a pool that had a really inadequate facilities for the amount of kids that were in the pool on any one session. It was always a race to the shower, or else a long queue for one. Then a struggle to find a cubicle to change in, as half of them were filled with people's belongings. There were nowhere near enough hairdryers, and if we could get one I'd usually cede them to girls with very long hair, even though DS has very thick, longish hair. So in winter, that meant bringing a big warm hat, just so he wouldn't freeze on the car journey home. If we didn't have a car, I don't know if I'd have kept him in lessons through the winter.
He also plateaued for a long time in the higher stages of group lessons. Not getting a dolphin kick just right, meant he couldn't graduate to spending more time building freestyle endurance and skills. Eventually I got sick of the whole ordeal, didn't renew at the end of one block of lessons, and enrolled both of us in a local gym with a pool - which worked out cheaper than a year of lessons for DS alone. Within six weeks, he was swimming multiple lengths freestyle, with tumble-turns in between, that I taught him from watching youtube videos. And I've no problem going there all winter long, as the showers are plentiful, the changing facilities lovely and always properly warm. We come out fully dry and comfortable every time.
I'd originally intended to book private lessons as needed, but so far, just the experience of being able to be in a pool whenever he wants, swimming for as long as he wants, having the time and space to swim consistently, has built his endurance and skill levels far more effectively than weekly 40 minute lessons. And we all come away feeling really good about it. (I've also gone from hating head-in-water swimming, to swimming 3-4 times a week, and reaching a goal of swimming 1km freestyle in a single session, though I still take a break every 100m or so and I do catch turns rather than tumble.)