In my experience some swimming teachers seem to be very hard on the young ones. I refuse to push DS with swimming. Firstly I don't want him to panic when he sees water as I think that counteracts what you are trying to achieve. Secondly I want him to want to swim. Thirdly I want him to trust me and make choices for himself when he can. Although DS is older than your little one I believe that learning principals are similar (in fact across most animals!). I would take them as far as they seem to want to go. I definitely would not be pushing them to the point where they are panicking no matter what the teacher wants. The more stressful the experience the less well they will learn. The more you can make it fun and exciting while picking up their cues on how they are feeling, the faster they will progress.