Even if you’re writing an in-class essay, it is important for you to make a rudimentary outline for your eyes only on the back of a spare sheet of paper. No matter if you are in History, English, or maybe even some crazy Common Core Math class, an essay will make a stronger essay if it is indicative of higher level thinking and organizational skills than if it is just a peacock’s tail feathers of knowledge.
This is not an absolute truth, but as you rise from a high school to a university student, you will be judged less and less on what you know and more and more on your ability to effectively apply it. However, sometimes you will be able to tell, or your teacher or professor will outright tell you, that the essay is meant for nothing more than to tell if you are paying attention in the class or reading the provided materials.
If this is the case, then the organizational strategy may make up less of your grade. However, there is never a case in which the teacher or professor would prefer a disorganized splublurp of information on paper to a well-organized and argumentative essay.