In the Autism communities, the terms “high functioning” and “low functioning” are used quite a lot. However, when asked, the communities are unable to agree upon defining criteria for each. This has led me to look for a clinical description for each, specifically for Autism. However, I was only able to find the Global Assessment of Functioning (GAF), which is not Autism specific but can be applied to all diagnosis in the DSM-IV-TR. 

The GAF does not use the terms “high” or “low” functioning, but uses a numeric scale from 0 to 100, based on a person's overall and cumulative rating in social, occupational, academic and psychological functioning. While it does include communication, it is not completely based on one's ability to speak. 

I recall that some of the community definitions used speaking and some used IQ as the defining criteria for functioning. However, there seems to be problems with that. For one, there are critics of IQ test results who say that IQ tests are only for measuring learning, not for assessing ability. Researchers have been critical of IQ tests towards Autistics since a lot of tests are language and cultural reference specific, and results are inaccurate. As for using speaking as a defining criteria, it has been noted that the ability to speak does not indicate ability to communicate and articulate, nor does it accurately represent abilities in other functioning areas.

As I found there is a lack of a clinical definition of Autism functioning levels based on criteria given by the communities, I can only conclude that it does not actually exist. If it does exist, it in inaccessible to the general public, and by extension, Autistic individuals, their caregivers and family members. 

So I have to ask, why are we using terms that have no official definition as a part of Autism diagnosis? Yes, it can be used as a descriptor for a person at that given moment, but the community definition is inconsistent and subjectively based on each person's experiences. This causes a lot of wrong impressions to be made about Autistic people, which can lead to belittling of people's experiences and difficulties as well as false assumptions of people's ability to grow and develop throughout life. It also has the effect of treating Autistic people as things that are not human and have qualities that need to be assessed, judged and graded in order to be of any value. This is rather dehumanizing of Autistics. 

What might be needed is not just a consistent definition of Functionality with High/Low descriptor tags, but an understanding of what a Functioning score means. We can use the GAF and divide it evenly into High and Low Functioning with a 50/50 split. However, this should not belittle the differences and disabilities of those considered High-functioning, since it takes a very high rating to be considered symptom-free. Looking at the criteria, there are very few people off the spectrum who can be considered that high-functioning. 

Furthermore, I have seen the term High-functioning used to ignore any reference that an Autistic has difficulties and to dismiss their experiences. I have seen High/Low-functioning used as if the terms were static statements of ability, that once given, are permanent. Such usage is contrary to the realities of Autism. 

Autism is a developmental disorder, which means that while development milestones are delayed or missed all together, skills do grow and are learned. We do not live in static bubbles, but interact with our environment, respond to events and situations. 

As such, a functioning rating is not a fixed fact, but rather an observation on one's social, occupational, academic and psychological abilities at the time of the assessment. This rating can change, depending on many factors such as medication, support services, various therapies and accommodations, as well as from personal growth and development. It is based on information and details that are extremely personal, and to make generalizations on it is at least very rude and hurtful to that person. 

Since the information used to assess a functioning rating is personal, an actual rating should be private and disclosing it should not be a requirement for participation within the Autism/Autistic communities. As a supportive community, it is inappropriate to make judgements and assumptions on the way a person presents, and on a person's functioning rating, should they choose to disclose. We also should not be using such changeable labels to discredit others. In fact, we should move beyond the labels and focus on treating Autistics as people, especially when they are willing to share their experiences and assist in whatever way possible, under their own choice, and in our mutual efforts towards self-advocacy. It is one thing to keep in mind a person's diagnosis, but another to make assumptions on confidential and private details of their lives.

If a person chooses not to disclose, that is their choice and as a community, we should respect that and not imply that they are less in worth. Instead, we should remain open and treat them no less or any different than before. As a community, we should be supportive of all our members.