I very highly recommend Lake Country Airways:
Lake Country Airways: floatplane training, endorsements, float charters and rentals A small and personal company, where you learn to fly in uncontrolled airspace, with lots of room, and beautiful scenery, but still near enough to Toronto for controlled airspace practice if you would like it. You can learn on wheels and floats, in 172's. I finished my commercial there years back. Very experienced instructors, and the company owns its aircraft. The school has an excellent relationship with the owner of the airport, who lives on site. You're definiatley not just a number at this school!