I have always felt that teachers are more dialed into the personality of the student body more than we know, but it becomes so burdensome to the mission of teaching that it is almost worthless to attempt much beyond the basics.

I saw this in policing quite a bit in later years. In fact, there were many times it was strongly encouraged that officers go find a parking lot to park in and only respond to calls. 

Then, there were people you just didn't want to deal with because of how they were just huge pains in the asses all around.

Still though, in our human form, I believe it is natural to want to gravitate to the bright and shining people no matter where they are and sadly, that is part of the problem. That those who need the attention don't get it and those who get it, don't always need it.

Here is an example - I have always been a good reader and I can remember back to first and second grade how frustrating it was to sit in class during a read-along by students when a student not as capable at reading took their turn.  And to me, these are the type of students that need the attention and attention given in a way that does not stigmatize (like making it obvious when a student needs more help - we need to be more gentle with such things).