Normal
Here's another passage from Primary Education (1959): "The 'Normal' As children grow up, the differences between them increase in every way. Even the youngest differ widely in their natural endowments, their upbringing and their experience, and these are influences which produce a great diversity of talents and temperaments among individuals and make each child a unique person. These differences and the diversity to which they give rise are not always obvious; they can only be discovered through patient study of individual children. Yet their discovery is supremely important for the teacher since they show how wide are the limits of normal development and how varied its forms. (...) It is quite normal for children of the same age to develop at different rates and for some children to develop quickly in some respects and more slowly in others. A child may be more gifted in art or music than in other fields, slow in learning to talk and to read but pr...