The big difference you will find from bondurant, skip barber and the like is that they teach you some basic skills and driving the line. There is SOOOO much more to road racing than driving "the line." In fact, I will say this, in a spec class, you will drive the line maybe 50% of the time.
If you want basic car control, Joe is right, you need to get some spacial awareness and improve your visual technique. In the spec class, you will have cars around you most all the time and you want to comfortable and predictible in that situation. There are some drills to do and things to practice to get used to this quickly. Again, as Joe stated, you don't want to be learning about your car on race day. The people around you will also appreciate that, too.
Also, there is nothing like a rolling, green flag start. You will want to experience that before you do it for real. It is absolute chaos at times and something you have to do to really understand it.
I seriously recommend the Driving Concepts race school. There, they assume you know the line and how to drive. They will help you have a successful race weekend in genereal. They will have you in close quarters, practice real green flag starts and simulated race situations, including flags....which is invaluable. They draw from years of sprint and enduro racing to help you learn form all the mistakes others have made before you. They will help you learn that your race starts before you get to the track and the value of preperation and much, much more.
Let me know if you have any specific questions about the school. It is really worth every penny!