Question: how many boxes of cake mix for a 10 inch square pan?
Answer: If you use the real cake you can eat some of it as a reward for the class and the good work. I use one box per 10" pan, so two mixes. If you use a cake dummy, you could wrap it in plastic wrap and then you could scrape off the icing and use it again. My instructor let us take in an 8" round, bigger if we wanted it.