If it makes you feel better, I accidentally sent the rough draft of my supplement to Cornell in which I spelled the word "its" as "it's" (it is) THREE times in the last sentence. I realized my mistake about 45 min after submitting. I called Cornell the next day and they said that it happens all the time and most people never realize it. They told me to just to send in the revised copy asap. The woman I spoke with said that admissions faculty reads the essays so quickly that most minor errors go unnoticed. She also said that they understand how stressful college admissions can be and that "most" essays have quantifiable errors in them. She assured me that a minor error or two in the essay will not derail an otherwise good app.
As far as how heavily they weight your high school record: I have been told that it is literally the least important part of your app. From what I understand, a stellar high school record has the potential of boosting your app, but lackluster high school performance will have little effect. This is all assuming that you have a few college semesters under your belt. The more extensive of a college record you have, the less your high chool record will matter.
Last edited by bellacose; 11-11-2012 at 10:51 PM.
Reason: added info