A child’s perspective is just that, the perspective of another child with their own spin on things. What makes you think a child does not have their own agenda at hand? That’s the problem here, a child is still a child. Maybe when they were younger there was an issue between them. Maybe subconsciously he remembers and disses the kid. Maybe there are only a few slots and he is rooting for his own friend or another kid? Kids are kids after all. What makes you think he is actually giving over his own perspective and not what he heard his old Rebbe say about the kid or what his parents said, or maybe because on of them said the kid is bad news he is agreeing and not sticking up for the applicant because he knows him on a different level.
Kids show off in front of each other to make themselves important. I can’t believe that you would put your trust in young H.S. boys to sway the opinion of the Principal. Its a game to them. They can say they don’t like a kid because he is fat, sloppy or has acne! Maybe because as a younger child he hated taking showers and he smelled bad or he didn’t like to share.
I think you are giving the kids too much credit here. I doubt that we are talking about Seniors because they probably wouldn’t know incoming talmidim, so it is most likely freshies or sophs. We are not talking about an older teen, more polished with a little more maturity and common sense.