Granted that I shoot a 1911, but I always take at least double the magazines suggested for the course. I also take a spare gun. Some gun schools like Thunder Ranch strongly recommend a spare gun and I have seen guns break in several classes.
I have never had too many magazines for a class.
"If you look through your scope and see your shoe, aim higher."
-- said to me by my 11 year old daughter before going out for hogs 8/13/2011