I have seen first hand the quality of the swim instruction at Kittelson Swim School in Fitchburg (close to Verona Rd). I just started taking my daughter there (she's 5), after just 5 weeks of lessons, she was swimming on her own. (Sessions are about 13 weeks long). I had taken her to other places for lessons previously (YMCA, Athletic clubs); the class sizes were so large and only a few weeks long, so there was no way she could possibly learn to swim on her own. Sorry, I don't have first hand knowledge of infant classes, but with the quality of instruction we received, I could almost gurantee Kittelson Swim School would be your best bet. I know a lot of their teaching is based on repetition. Check out their website for more info. The classes may be a few extra dollars per class, but it is worth every penny.