A Suggestion for College Admissions Offices
The SAT essay is written in pencil by students whose previous writing experience is probably on a word processor. It is graded by the sort of mechanical standards that you have to use if you want comparable measures for millions of essays graded by (I'm guessing) tens of thousands of graders. One result is that, so far as I can tell, colleges do not put much weight on that particular piece of evidence.
Application essays have another, and potentially more serious, problem—the college has no way of knowing who wrote them. They may represent the work of the student, they may represent the work of his parents, they may represent the work of an admissions adviser paid by the parents to help get their kid into a good school. Even if the student sending them in played some role in the writing, the college has no way of knowing how much what they are getting reflects his ability, how much editing by others.
There is a simple solution to this problem, one which no college I am aware of has used: Have the applicant write an essay that they know is his. Put him in a room with a word processor—also pen and paper for those who prefer to write that way—and a short list of possible topics. Give him an hour and see what he produces. That should sharply distinguish applicants who can write coherent and grammatical English prose from those who cannot and, less sharply, distinguish the minority who are actually good writers.
The mechanics of the proposal should be pretty straightforward. Many applicants visit the colleges they are applying to, take a campus tour, attend a presentation by the admissions office, perhaps have an interview. For those, all that are required are a few rooms in the admissions office provided with computers.
What about students who do not visit, perhaps because they live far away? Colleges have alumni, and use them in the admissions process, often to interview such students. Alumni have computers. Arrange, in each region of the country from which students apply, for at least one alumnus to invite applicants to demonstrate their writing ability.
Once such arrangements become reasonably common, it should be possible to do the same thing in a more organized form, with someone in each major city in charge of supervising such essays on behalf of any college who wants them.