Why should the consent of the parents matter when designing the curriculum? If the parents in an area suddenly decides that they all believe the earth is flat, would you be okay with that being the science education?
And if a bureaucrat decides that flat earth theory must be taught to kids would you be ok with that being the science education?
It's the difference between a state run economy and a capitalist one. Of course the capitalist one is not infallible but it has been proven time and time again to provide better results over time.