Because when they control an expenditure via a statutory scheme, they surely won't control the definition of the things the money is expended on, and thereby control the thing itself, i.e. "education."

The problem with people like OP is that they can't imagine the world to be any way other than what they experience. For example, he thinks the "education system" is a fixed, immutable thing, and not the result of various societal forces that have and will continue to change over time.