Seconded. In retrospect, the Canon teaching of potions now seems incredibly practical. The vast majority of students not only don't need to learn the theory, but it's a negative for them to do so. They only need to learn two things: 1) how to make the potions they'll use every day and 2) whether or not they even can make those potions or if they should just buy them from someone else. Constant repetition with minimal instruction is exactly what you need for a class that's more akin to cooking instead of calculus.