The main purpose of any education on any subject is to teach its tenets of which that foundation, in order for it to be sound and right, must be built upon truth, and nothing else. This therefore means that our educational system has an obligation to first know itself, and then to impart such knowledge through books and teachers to its students so that they can properly assimilate the subject matter. When it comes to subjects such as the English language and its correct structure, or mathematics and its laws, these subjects are both well known and have little controversy attached to them, for these have specific fixed rules and principles attached to them that are well known, uncontroversial, and must be well learned in order to know the subject matter.
On the other hand, there are many subjects that are in some sort of flux, such as various religious beliefs and creeds, as well as evolution in all of its many forms and guises, in which different beliefs affect the very processing of such information and different cultures teach us different things. In any subject, in which the information being imparted cannot be definitive because these are essentially reasoned suppositions, or interpretations through the prism of one's given viewpoint, or general theories; such subject matter, should be discussed in a manner that recognizes, that such a thing as truth on these subject matters, is elusive, because it cannot be known for an absolute certainty, so such teaching must take into account that these subject matters require thinking, discernment, and an open mind.
The overall purpose of education is to see that fundamentally all students are proficient at a level that makes them functionally literate in their society and further, that they are able to think and reason in a manner that allows them to apply their learning successfully to their life, and especially to their present-day concerns and duties. For if you are unable to take such education that has been taught to you, and successfully apply it in the world at large, than such education has little utility for you and does not benefit in whole, the society that you interact with on a day-to-day basis.
This then sends the very real message, that education at every level and at every turn, must relate what is being taught in class to the actual real world, for it is in the application of this knowledge, that proves whether such education has been successful or not. After all, if students are unable to relate facts, theories, history, music, and so on and so forth, to their circumstances that they deal with in the outside world, than that education has not properly been assimilated.
This means that all students that are functionally illiterate, have failed by their educational system. So too, those that are unable to successfully apply their knowledge in a manner that permits them to advance in their personal as well as their work lives has not been successful either. It is in the application of education that proves or disproves whether such has been successfully comprehended or not. It is of vital importance that education imparts a firm foundation for as many as possible, because those that are unable to think and reason properly, or are unable to discern well between truth and deception, are vulnerable to the unscrupulous that will exploit them for their selfish benefit, again and again.