I think vouchers are a good idea. They would help bring down the cost of education. But I am not surprised that more people responded to your second idea, "The oil companies are not an example of the free market at work." People like to criticize the large salaries of CEO's and business executives. After all, creating class envy is easier than coming up with a cogent defense of the argument that teachers are underpaid.
Do you really think vouchers are the answer? Just my own thoughts, but it seems to me that private schools are known to be high achieving schools because of their exclusiveness-consistent small class size, well rounded similar backgrounds, and let's face it-big bucks! If you start throwing vouchers at people, what's that going to do to these private institutions? I wonder--would the private schools be able to maintain their high achievement scores/bragging rights? Wouldn't it make private education--well--public??