Mental retardation may be defined as mild, moderate, severe, or profound, depending on a child's IQ scores and functioning (American Psychiatric Association, 2000). In schools, intermittent or limited supports are commonly provided for students with mild mental retardation. The table below summarizes the IQ scores for the different levels of mental retardation and describes four levels of support that may be provided (American Association on Mental Retardation, 2002).

Level of Mental Retardation Range of IQ Test Scores and Levels of Necessary Support
Mild mental retardation

IQ score: 50–55 to approximately 70–75

Intermittent supports are provided on an as-needed basis.

Students do not necessarily require continuous or daily support.

Moderate mental retardation

IQ score: 35–40 to 50–55

Limited supports are provided over a prescribed period of time.

Intermittent and extensive supports may be necessary for some students as well.

Severe mental retardation

IQ score: 20–25 to 35–40

Extensive supports are provided, usually involving assistance on a daily basis in a number of settings.

Profound mental retardation

IQ score: Below 20–25

Pervasive supports are provided usually involving constant assistance across all environments, often of high intensity and may include life-sustaining measures.