A state school is a product of our social system. Therefore state school is ultimately designed to produce citizens who will be productive yet dependent members of the system (Someone who will always require a regular paycheck from a company or institution to adequately sustain themselves). It is in no way intended or designed to promote the mindset required for an individual to advance to a position where they can exist outside or beyond the system (Someone who has acquired enough wealth or positional authority to have independent control over their financial future). This is not by any sort of conspiracy, but simply the natural progression of an educational system provided by society for the purpose to benefit society. There are always exceptions, but I have never attended or encountered a state school that encouraged "individual thought" amongst the majority of it's student body.
With private schools education is a business. Fortunately the best business' are the ones that produce the best products. In this case the best product is the right sort of education. When it comes to exams, often "good" state and private schools have similar results. Exams only reflect academics, and that is mostly all a standard state school is designed to provide. The reason many state schools seem like mere exam factories is because they are, by design. Academics are usually necessary, but far from the most important element of personal success. The right private schools are so much more. The best examples I've seen involve their students in leadership, mentorship, innovation, facing adversity, networking, arts, culture, community, etc.. Most importantly the right private schools promote it's students to think beyond the system. State schools don't teach that because they are interested in the masses, and such ideas and behavior are not beneficial to society when exhibited by the masses. It is a state school’s function to promote the status quo. The right private schools promote exceptionalism.
This is not an argument for eliminating the private school option. Many would like to argue that this disparity facilitates social inequality. I however can’t conceive of an alternative that wouldn’t perpetrate an even greater injustice against our liberty to utilize our personal resources as we see fit. I would prefer to not waste time considering the fairness of it all, and instead focus my energy on using every available resource to obtain the best private education for myself and my children. If this ambition proved to be unobtainable, as it certainly would for some, I would seek provide the right education myself as best I could to address the areas that state schools deliberately neglect.
I went to state schools and I quickly developed a distrust and skepticism for the overall curriculum which has served me well. I would advise all students, especially those who attend a state school, to consider yourself to be solely responsible for your proper education. At least that is the advice I would give to those few who expect more from their career than a 9-5 obligation, and a decent salary.