The
height of the chair, in relation to the student and the
height of the desk, is the most important factor in
correct posture; so try to have a
range of chairs in different sizes, preferably with
height - adjustment mechanisms.
Size is important but not as important as function, so if you have a dog in the
correct height and weight
range but with other faults compared to a dog without those other faults but smaller or larger than the ideal
range, the more
correct but smaller / larger dog should win.