The Cookworks is the cooking school arm of Mildred Pierce, a very nice restaurant in the neighborhood. I've only been there for brunch, but I've been there for brunch a number of times, and they do it quite well. There's only a little variation in their menu which is why we don't go there more frequently. Classes which particularly caught my eye at the cooking school include their two day sauce workshop, their French Bistro class, and, of course, brunch. The brunch course teaches several of the dishes that the restaurant makes and includes a free cookbook, one I've seen for sale in William Sonoma before.
The Calphalon Culinary Center, at King and Spadina, is a cunning way for a cookingwares company to advertise under the guise of informing. That said, their class offerings were focused enough to catch my eye. Knife skills and Thai food were the two workshops I considered there, both of which received enthusiastic endorsements as topics from my voters here. I've signed up for knife skills because a skills class is the more sensible choice, but I might still give in to temptation and enrol in a Thai cooking class (although they're also available at The Cookworks).
Bonnie Stern's Cooking Classes look to be run out of the titular chef's cooking store, at Yonge and Eglington. Moroccan food, Rustic Italian, and cooking with a celebrity chef (several options) were my picks from the class selection there. The store also hosts culinarily-related book signings.
There are plenty of other places to study food-making in town, from culinary schools designed to train professionals to places specializing in desserts, such as J.S. Bonbons, whose Intro to Chocolate Making class triggered my whole interest in this subject.
Note: Most class prices range from $50-$150 for 2-3 hours.