Multiple problems with this. The most obvious one is cost: schools don't have large classes because they want to but because of budgets. The second one is that "consumer" sounds like an insult in this case and might very well be: experience in other countries shows you that parents tend to optimize for grades , test scores and "connections"; so you get grade inflation, "teaching to the test", bribery and networks and over all worse quality (just think of prejudices you have heard about some private schools).
Irrelevant to the question at hand. There are small schools with small classes, small schools with large classes, large schools with small classes, large schools with large classes.
> "consumer" sounds like an insult in this case
No, it's intended to be a technical/neutral term to describe the person(s) making the economic (as in the science of economics) choice of which school to choose.
> parents tend to optimize for...
And other parents optimize for other priorities, see e.g. Montessori schools, St. Anne's in NYC where there are no grades. Having options allows parents to make that choice. When parents are forced to send their children to the large monopolistic public option because there are no other affordable options, they don't have a choice.
