Or perhaps you were thinking of the Three Degrees of Stupidity, whose creator I know not but whose work I reproduce here for comparison:

Class Three: High Function Stupids – Cognizant Stupidity
Cognizant stupidity involves a particular and localized lack of intelligence. This is generally transient but clearly noticeable. Such people are often taken advantage of- primarily because they have something to lose. Most cognizant stupid people function well in society. It takes some time to determine their stupidity – they can be lucid for prolonged periods of time.

Fools are the most commonly and widely dispersed of the type. A Fool, also known as a Dupe is someone whose stupidity lies in a narrow area. Some Fools are often mistaken for intelligent people who are ‘fatally flawed’. Foolishness can be rewarded in society, however that doesn’t quite make up for the lack.

We often also encounter Idiots, who function quite well in society, but there are a class of things they just don’t get. Idiots are generally smart enough to avoid their own idiotic behaviors, but they have a surprising amount of tolerance for their own idiocy, which they can sometimes convince others as ‘unique genius’. Idiots are particularly annoying because they generally believe that they know what they’re talking about even after it becomes clear that they don’t. They will call it a ‘difference of opinion’, but they’re simply idiotic.

Stooges- at the low end of the cognizant totem pole- never quite avoid stupidity. Stooges, however, are intelligent enough to use their stupidity to their own advantage, and usually are most recognizeable by their capacity as Flacks, Namedroppers, Flunkies and Brownnosers. Stooges are deceptive by nature and function best under the color of authority. Stooges, once discovered, do what they do best, blame somebody else.

Class Two: Low Function Stupids – Chronic Stupidity
Chronic stupidity manifests itself in a variety of ways, however a chronically stupid individual is almost immediately recognizeable as challenged by ordinary life. As low function individuals, they are generally found in co-dependent relationships with each other or sympaticos.

The classic LFS is a Doofus. Easily recognizeable, a Doofus has difficulty making sense of common social conventions, such as dressing properly, laughing without snorting, or using breath mints. A Doofus who sees you tomorrow will retell the joke you told him today. As a social incompetent, a Doofus aims to be a geek, but alas is too stupid to convince anyone save perhaps their poor suffering parents. At the same level of a Doofus but with an emphasis on physical stupidity is a Spaz.

However there are fairly stupid people who do manage some ability to pass themselves off as socially acceptable, that is until they open their mouths. Meet the Airhead, also known as the Twit. Both are capable of talking at a reasonable speed but are they saying anything? No. These stupids are remarkably unselfconsious about their stupidity, but that is because they generally are able to seek and find each others company. If you know more than one Airhead, check yourself.

Also very common are Dolts. Also known as blockheads, knuckleheads, and shitferbrains, Dolts are generally incapable of thinking on their feet. Dolts have one-track minds which can make them fairly good athletes, thugs, and/or gas station attendants. A dolt has a favorite song and she’s always singing it. Dolts never get over the death of a pet or Curt Cobain.

A Doofus who is also a Spaz is generally known as a Moron. Morons are at the bottom of the low function chain. Morons tend to remain out of sight and out of mind, but they can make their presence spectacularly known. Driving on the sidewalk is a moronic activity, as is setting fire to cats. Most winners of the Darwin Awards™ are Morons.

Class One: The Pathological Stupids – Terminal Stupidity
Uh, what can I say? These are a group that one doesn’t often encounter in the mainstream of society, however there are many who remain uninstitutionalized. It is not generally considered polite to discuss the behaviors of the PS crew, but who gives a fart about that?

The most charming of the Pathologicals is the Imbecile. Imbeciles generally have sunny personalities, which means that they can smile without drooling. In the company of an Imbecile, most people are pleasantly surprised that they can do anything at all. In fact, imbeciles are about as bright as 7 year old children. Give them cookies, but when they start talking about ‘doody’ it’s time to leave.

The most common of the low end are Retards. Retards have a hard time maintaining any train of thought whatsoever. Not only do they speak in non-sequiturs, life itself is one stream of non-sequiturs for them. Although it’s snarkily cool to call someone a Retard, as I am prone to do, true Retards need personal attention at all times and must be kept away from sharp objects.

Cretins are the lowest of the low. You’ve never seen one, and that’s a good thing.

I wish I knew who created that list, so I could give them proper credit.

I did a search for stupid scale and I got this:
http://www.urbandictionary.com/define.php?term=Stupid+Scale
I do not like their scale, as profanity is not descriptive enough to properly scale stupidity.

How about having a go with subdividing stupid?
Top 10 lists are popular this time of the year….
-pf