Special education carries a special sort of stigma about it. As much as we all know that every child (and indeed, every person of every age) has their own individual set of both strengths and weaknesses, we also all know of the intense additional scrutiny that students who find themselves in “special” classes get branded with. For those types of children, every day results in still more teasing and mistreatment than is the norm for most kids. All sorts of different stigmas plague such students, who are often considered by their peers to be stupid and incompetent.
While these students all have their own deficiencies, the students who are in special education classes are simply the easiest targets for the other students to pick on. It is extremely obvious when a small group of students separates from the larger group and goes off to a small room for the purpose of academic remediation. And when there is an obvious difference, kids latch onto it like pitbulls going after a piece of meat. While there is nothing that we as adults can do about this social tendency of children (which we all have, as well), we can do something to help the students in this situation to cope with it more effectively.
If your students have gotten into the depressive funk which tends to accompany being in special classes, your job is to help them to get better at whatever they are lagging behind in, so that they can rejoin their peers as fully respected members of the group. Only when they are perceived as the same will the excessive teasing stop. And when this happens, their self confidence will return to them in full bloom.