Intellectual disabilities can be divided into three "categories." Some cautious generalizations about learning can also be made.
88% of people with an intellectual disability (the vast majority) fall into this category.
People with a mild intellectual disability may just seem slower than the rest of their class in schoolwork and learning. They are able to take care of their personal needs and have the communication skills necessary for independent living or at least semi-independent living.
7% of people with an intellectual disability fall into this category.
People with moderate intellectual disabilities may learn to talk, to read and write a little, to travel independently and to manage their activities of daily living, given appropriate training, education and life experience.
4% of people with an intellectual disability fall into this category.
These individuals may learn to talk in simple sentences and may reach independence in dressing, eating and otherwise caring for their own physical needs. They may also learn to read a few words or symbols.
Ability Incorporated [http://www.ucaqld.com.au/disability/id.html]