I have had two kids get in. They went to a large competitive public high school. It’s my suspicion that admissions has a preference for these schools.
At least when they got in, UT gave applicants two scores. One, being scholalastic (test score, GPA, class rank) and the other being holistic (essay, resume, references etc).
These are some things I learned:
Get someone to help the kid with their essays. If nothing else it keeps them on task so it’s not all crammed in and rushed. It should be a process and written over time which allows for further thought and just a better overall presentation.
Get some work experience in the field that you are applying for a major in. Does not have to be a 9-5 job. Maybe it was just an unpaid internship during the summer. Or, ask someone in the field if they can shadow them for a couple of weeks and call it an internship. They seem to like kids who show some interest in their field by actually going out and learning something about it.
My kids actually started a small business selling some things that they were making. Had them in some stores locally. Not a huge deal but it did make their resume tie into their proposed major.
Encourage your kid to try for a leadership position in any student group they are in.
You should also prepare them for people that they know who appear to be less qualified academically to get in. It really all comes down to how competitive their major is. Comparing the average stats needed to get into business vs social work is really apples vs oranges.
Letters of recommendation are worthless unless they come from a teacher who has greater than normal insight into the student and can offer some unique perspective.