They have been deprived nutritionally, or some illness has not been picked up, or they have not been screened for vision or hearing defects, or they have not had some kind of a chronic illness or error of metabolism picked up.

If you have a kid who goes to kindergarten and doesn't know what a circle is, doesn't know what red and green are, and doesn't know what right and left are, by the time he learns those things, the rest of the class is far ahead of him.

When a child shows up for school, and is not physically and mentally ready to learn, he or she never catches up.

C. Everett Koop Quotes