We have had our 3 year old at COTS (Children of the Sea) for over a year now and he has been in 3 sessions so far. We previously had been at Le Petit Dauphin, which was not a good school (lacked basic instruction, lots of staff turnover, poor class structure), and also at the Salvation Army Rec Center in North Portland swim school (which was excellent also, but too far away from us in Tigard). COTS has a very good structure and goals for each type of class for the children. They are required to meet certain criteria before they advance to the next level. Each class is fun and the instructors are very good and experienced at working with the kids. It is a bit spendy as these things are, and the classes fill up very quickly, but if you want good swim school, I can highly recommend.