The quiet student may never let you know that they have a question and may never disrupt the class, but we miss out on their ideas by ignoring them.
The talkative student may constantly distract the class with thoughts about far-flung topics. Wouldn't it be wonderful to have that same energy directed to the matter at hand?
The disrespectful student may insult you and embarrass you in front of the class, but do you think the mathematics is really what made them upset?
The successful student may be constantly praised and use this success to skirt around the school's discipline. How will they fare when they are corrected in a job or by a loved one?