Most people know someone with special needs. The person may have a handicap that affects the mind, sight, voice, or even how a person walks. We have all seem ableism in action also at some point I believe. the use of the word retard is an example. We expect those who are handicapped in one way or another or have special needs to not be a good of a contributing member of society  as the student who has zero flaws. In a way we give up on these students when we don't expect them to accomplish anything substantial in their lifetime except to be a human pin cushion for doctors. It is a disservice for all those who are deemed handicap in some form because we do not give them a chance to show us what they can do. Instead they live up for the self fulfilling prophecy given to them by doctors and old fashioned school teachers.
We expect less of those students, and thus do not always give them work or concepts that could potentially open their minds. In expecting less of those students, we do not take time to discover their own personal intelligence.; Like the article said, their are an infinite possibilities for types of intelligences. With no goals, or push to find and enhance these intelligences, the handicapped students become lethargic from under stimulation.
There are some handicaps that are not handicaps at all. When a student is deaf, or mute, the student has every chance to be able to succeed if they are advocates for themselves. According to Hehir, ablelism in the classroom happens to these students because of the teacher's teaching style. Oral teaching is an  ancient and well respected way to learn. If the teacher does not speak American Sign Language, (ASL) the teacher will rely on lip reading for the student to understand the content of the program. The teacher then forces the student to learn lip reading over American Sign language. In a way is it silently telling the student their way of learning and communicating is not good enough.
Students who have IEPs for their learning disorders have certain parameters and rules for the teacher to follow. Yet, could there be instances of teachers making modified lessons, class work, or evaluations too easy? I think so if certain teachers don't believe their students can and are able to accomplish harder tasks. It is kind of like the ableism students who are  physically handicapped face. Those who have the ability to help them grow up into a productive member of society.