Actually, many years ago two key aspects were computerized:
1) Financial aid: Students filled out a standard computer-scan questionnaire which was distributed accordingly. 2) SAT scores -- presumably now sent electronically to colleges.Different school districts have greatly varying ways of preparing transcripts of high school life. Some are not computerized at all, some are highly sophisticated. The information includes more than just courses and grades, it also includes evaluations, extra curricular, discipline, attendance, etc. I think schools vary on what info they send and colleges vary on what info they want.
If I were a student today, I'd be quite nervous about hackers or others getting into the data.
Also, I don't want to encourage large colleges from using computers to do basic application screening. I realize that in effect is done now manually due to high volume of applications -- a clerk does a quick scan looking for basic minimums, but having a computer do it is worse -- it removes important variables.
Grades are very subjective and vary tremendously from school to school. A yuppie ambitious suburban community will have a very intense school district where an "A" really is an "A". In contrast, a weak area might give an "A" just for showing up every day and not causing any trouble. When I got to college a lot of my fellow freshmen were overwhelmed by the coursework. They got straight A's in high school easily but college was much harder. A "C" student from an intense high school would be more prepared than an "A" student from a mediorce high school.
The point is that grades in themselves are not enough -- the kind of school is important as well, as well as other factors. Computer scanning is not good at that subjective sort of thing.