Here is what the IIT entrance process was like, when I went through in the early 80s.
1. Take entrance exam - 4 session, math, physics, chemistry, english, a couple of hours for each over 2 days.
2. Wait for results. You get a discrete rank - one through around 2000. There were 6 IITs when I was there, about 300 for an incoming class at each, so total of about 1500-1800 incoming freshmen.
3. One fine day, show up at your nearest IIT and fill out a card listing your choice of campus and engineering field in order of choice, one through 10 or whatever.
4. And this where things get surreal. Ever seen an NFL draft? That's what it's like. Everyone is in a big auditorium, that is linked by a conference call to the other campuses.
5. They go - Rank 1, what do you have? Computer science in IIT Bombay? OK.. Rank 2 - what's your first choice? Computer Science in IIT Madras? OK.. and so on. Computer science was the most desirable, so by the time they got to rank 100 or so all the computer science seats were gone. Then came electrrical, mecahnical, etc. etc. So, if you were rank 500 or so you probably didn't get your first choice.
There were no recommendation letters, no school grades (you had to graduate, that's it), no AP scores, nothing. It was the entrance exam period.
I'm not saying it was the best system, but it was brutal and agnostic for sure.
And then it got harder when you got in lol...