Editing College Essays is Complicated
The college essay is considered one of the most important aspects of your entrance application. While scores, grades and reference letters are also heavily counted; the essay is what will set you apart. Gone are the days when writing about how you will save the world is going to get you noticed, the expectation is that your college essay could be someone's commencement address in the future. College essays are held to a very high standard, which is what makes editing college essays so complicated.
The Style
Getting the style right is the first factor. If the tone and clarity of you voice is too casual or too distant, it can adversely affect your admissions. Most high school students are only familiar with writing in an APA format which has done little to train them about the nature of voice in writing. The correct tone is one of self-confidence and humility. Knowing what words, phrases and even punctuation contribute to that tone is a skill that can be difficult to master. A good editor can spot when a simple word choice has changed the reader's entire perception of the author in a negative or positive way.
The Construction
If you have spent the past 4 years writing 5 paragraph essays then you have a basic familiarity with the construction expected of a college essay. That construction is only considered the skeletal framework. The college essay is expected to have its own circulatory system and muscles as well. Good editing will spot pedantic transitions and when you can break out of the mold to add or drop a paragraph. The goal is to shape the essay to present you, not vice versa.
The Mechanics
Writing mechanics go beyond grammar and spelling to active and passive formulas. If you have an entire essay that is written with dead endings, you are going to leave a series of very unenthusiastic readers on the admissions council. Being able to spot the interplay of syllable, conjunction and pattern is a part of mechanical editing to keep an essay as lively as possible.
The Content
While the content is yours and yours alone, often drawing from your life experiences and personal goals, the logic is quite global. If you don't make logical sense, you will not be thought of well. Making sure that there are appropriate transitions and lead, as well as carefully crafted foreshadowing can transform the content from a recitation to an engaging narrative.