Asking a horse to do something and having him do it is success, and success builds confidence. I have had horses most of my life. It is such a wonderful feeling to achieve what you are asking of a horse no matter if it's a jump or just asking for them to do something simple. It's a constant learning process for horse and rider.
I think there might me more to this. This is a school horse, right? He seems to have this same issue with others in the class also. He probably has gotten away with this and the program seems to be going his way. The instructor or stable owner might want to put a bit of time on him themselves for a little attitude adjustment. As a student you need to learn how to ask for and get the desired response but while you are learning you don't need to be frustrated by a sourpuss. Just something to think about.
Good luck to you and enjoy the ride.