In preschool-age children (up to 5 years old), intellectual disability is classified at one of the following levels:

• The child can develop social and communication skills. There is minimal retardation in sensorimotor areas.
• The child can talk or learn to communicate but has poor social awareness and fair motor development. The child benefits from self-help training and can be managed with moderate supervision.
• The child has poor motor development with minimal speech and little or no communication skills. The child is generally unable to benefit from self-help training.
• The child has minimal capacity for functioning in sensorimotor areas, and requires nursing care, constant aid, and supervision.

In school-age children (6 to 20 years), intellectual disability or learning disability is classified at one of the following levels:

• The child can learn academic skills up to approximately sixth-grade level by the late teens, and can be guided toward social conformity.
• The child is unlikely to progress beyond second-grade level in school. The child can benefit from training in social and occupational skills, and may learn to travel alone in familiar places.
• The child can talk or learn to communicate, can be trained in basic health habits and other functional habits. The child is unable to benefit from vocational training.
• The child has some motor development and may respond to minimal or limited self-help training.

In adults (21 years and above), an intellectual disability is classified at one of the following levels:

• The individual can usually achieve social and vocational skills for minimal self-support but may need guidance and assistance when under unusual social or economic stress.
• The individual may achieve self-maintenance in unskilled or semiskilled work under sheltered conditions but requires supervision and guidance when under mild social or economic stress.
• The individual may contribute partially to self-maintenance under complete supervision and can develop self-protection skills to a minimal useful level in a controlled environment.
• The individual may have some motor and speech development and may achieve very limited self-care but requires nursing care.