I'd also say by 5.30 he's probably more ready for a sleep than a swim. The school day is so wearing for them at that age. My dc do have a swimming lesson at 5.30 on a weekday eve so I feel your pain- mine are 7&9 and can cope, I still think my 7yo is doing well as she's quite tired by then. Also as a swimming teacher I'd say there's not a mass of difference to their learning (as opposed to our own peace of mind for their safety) if they learn at 6 rather than 4. If hrs knackered leave it til Summer or next sept IMHO
My 4yo started school in Sept and was moved up to Stage 2 in his swimming lessons with a new teacher.
I was called over after his lesson yesterday as the teacher as she was a bit exasperated about his lack of co-operation and general zoning out. basically he won't kick his legs - or won't do as she asks to improve his kick. He does find using a float and kicking on his front hard. And I don't think its all lack of co-operation, but half is not really fully getting what he's meant to do.
I tried to find an earlier class (its at 5:30pm - not ideal at all, but only one that can also fit in my other DC with his teacher), but there isn't anything. I will also go at the weekend to 'work' on his kicking. But I wonder whether I should be ditching the lessons/trying again in a few terms, or trying to find a different teacher (nothing wrong with her, but maybe they just don't gel well), smaller class sizes (8 in his class)??