At first glance you should use Col. C. You are correct.
However, as I think about this, you have an additional problem with a learning facility: At this location, unlike any other, you have a very high probability that all of the ovens will be turned on at exactly the same time when the instructor says, "Preheat your ovens to 375*, and while you are preheating prepare your sauces on the stovetop." I think an engineered solution to this problem is in order--or more likely, someone else on this forum has done a job like this and knows what to do.
McClary's got a different code book than I, but has a better idea: use the commercial table 220.56 Add 'em all and apply .65 demand factor.