When Locke discusses the methods of education used by the schools, he is speaking from experience. This entire section of the book is an implicit criticism of the education he received at Westminster and Oxford. Locke hated his time at these schools, and did only the minimum amount of work necessary to get by. He spent the rest of his time on extracurricular academic pursuits, studying medicine, chemistry, philosophy, and politics on his own.
Locke's horrible experience in school was in large part the motivation for writing the Essay Concerning Human Understanding. For centuries, the schools had been dominated by a group known as the Scholastics (it is not a coincidence that these two words sound similar). The Scholastics had held control of education and of academia in general since the middle ages (actually, they were not only in charge of the schools, they had founded all the schools in Europe). Their main activity was interpreting the works of Aristotle, and solving minor problems that arose from those works. In Locke's opinion they favored obscurity over clarity, details over the larger picture, and, to top it all off, they hid behind piles of meaningless jargon. Other thinkers held this same opinion, and by the time Locke reached maturity there were new schools of thought emerging that took a very different approach to knowledge. The most successful and famous of these was the Cartesian school of thought, founded by the French philosopher Rene Descartes. Descartes attempted to provide a crystal clear, perfectly reasoned picture of the world, in which the entire physical universe is a machine, operating based only on the principles of matter and motion.
Descartes had a very specific mechanistic picture of the world; others began developing alternate mechanistic theories. One such thinker was the scientist Robert Boyle, who Locke befriended while at Oxford. In Boyle's home Locke met other mechanistic scientists, who were all trying to explain the physical world in clear, rational ways, and basing their ideas on observation and experimentation. Locke was extremely impressed with these men, and quickly made himself an integral part of their world. He wrote the Essay in order to provide a philosophical basis on which to rest the new science of his friends. A major goal of the Essay was to show the folly of the Scholastics, and of much that is taught in the schools. Locke, in other words, had a long history of antagonism with the schools, so we should not be surprised to find him very critical of these institutions in Some Thoughts.
Locke's stance against poetry can be seen as another symptom of his anti-nature prejudice. While he allows that some people are born with a talent for poetry, he does not allow that this is an inclination that should be encouraged. Once again, in other words, he does not allow for the fact that people are born with inherent preferences, in this case strong, life-determining passions. It does not occur to him that some people might not be happy in the life he is proscribing (a life concerned only with business, politics, and good manners), and that some people might have overwhelming artistic desires.
Locke bases his plan for language education on the principle that foreign languages should be learned through the same method by which we learn our native tongue. Locke might be right that conversation is the most effective method by which to teach a foreign language. However, recent discoveries in linguistics make the question a more complicated one. While we cannot blame Locke for thinking that all language acquisition takes place by the same mental process, there is now much evidence to suggest that something very different is happening in our minds when we learn language as a small child, and when we later learn a foreign tongue.