While there have been many critical debates over the correct and valid construction of prose, the reason for its adoption can be attributed to its loosely defined structure which most writers feel comfortable using when expressing, or conveying their ideas and thoughts. It is the standard style of writing used for most spoken dialogues, fictional as well as topical and factual writing and discoursed. It is also the common language used in newspapers, magazines, literature, encyclopedias, broadcasting, philosophy, law, history, the sciences and many other forms of communication.
The major factor in writing an essay, which contributes to your high score, is undoubtedly your competence and proficiency in written English. You should acquire scholarly and literary writing skills. The simple rule is that you should be able to write a sentence having grammatically correct structure. Grammatical accuracy refers to usage of words (. verbs, nouns, adjectives, phrasal verbs etc) to make a correct sentence. Hence, you should study the basics of grammar in order to express your ideas in Standard English. Besides that, idiomatic usage in writing makes your essay look attractive. You should use a wide range of vocabulary. If possible, avoid the informal words or very common words; rather use formal words and appealing words.