Another awesome quote from the essay

"Expectations affect students in many ways, not just
academically, but in the form of mental and social deprivation which
causes a lack of self-esteem. When educators receive information
about students, mostly even before the student walks into their
classroom, from past test scores, IEP’s, and past teachers, it tends
to alter the way we look at the students potential for growth. This
foundation of expectation is then transformed on to our method of
instruction.
One basic fallout from these expectations is the amount of
time educators spend in communicating with students. We tend to speak
more directly to students who excel, talking in more matures tone of
voice, treating them more like a grown-up than we do to the students
who are already labeled underachievers. This can give the student an
added incentive to either progress or regress due to the amount of
stimulation that they receive.
As educators we tend to take the exceptional students "under
our wing". We tend to offer knowledge in situations to help push the
good students, in comparison to moving on to the next task for the
others. We also tend to critique the work of our god students more
positively than the others, offering challenges to the answers they
have given.
The most obvious characteristic that educators present to the
students is in the area of body language and facial expression. We
tend to present ourselves in a more professional manner to our good
students, speaking more clearly and with a stronger tone of voice. We
tend to stand more upright, in a more powerful stance, than to the
slouching effect we give to the underachievers. The head shakes,
glancing with our eyes, hand gestures, and posture all contribute to
the way we look at certain students based on our first impressions
which came before we even knew the student."
Taken from http://www.cyberessays.com/Politics/31.htm

It's crazy to me how even the most subtle body language can send a message to students showing favoritism. Teaching is one of the most difficult forms of communication, in my humble opinion.