First, high school starts with 14 year olds, not 10.
Second, people don't suddenly learn how to write a competent essay at the last minute. Writing a good one is a combination of many skills learned over many years.
BTW, I did not take any college prep courses prior to Caltech, and found myself way behind the other freshman who did. I found out many years later that the admissions committee had taken a chance on me, and they were very nearly wrong. I came that close to flunking out.
If public schools dump their gifted tracks, inequality will only increase as the top schools will wind up drawing only from private schools.