tical units, all children are different. They differ in
physical, in mental, and in spiritual qualities. Their hair is different
in color and in texture. Their feet and hands vary in size. Some
children are apt at mathematics, others at drawing, and still others at
both subjects. Some children have a strong sense of moral
obligation,--an active conscience,--others have little or no moral
stamina. No two children in a family are alike, and no two children in a
school-room are alike. After an elaborate computation of hereditary
possibilities, biologists announce that the chance of any two human
creatures being exactly alike is one in five septillions. In simple
English, it is quite remote.

IV The Five Ages of Childhood

A very ingenious statement of the case is made by Dr. Bird T. Baldwin.
Children, says Dr. Baldwin, have five ages,--

1. A chronological age,
2. A physical age,
3. A mental age,
4. A moral age,
5. A school age.

Two children, born on the same day, have the same age in years. One is
bound to grow faster than the other in some physical respect. Therefore
the two children have different physical ages, or rates of development.
In the same way they have differing mental and moral ages. The school
age, a resultant of the first three, is a record of progress in school.
Even when children are born on the same day, the chances that they will
grow physically, mentally, and morally at exactly the same rate, and
will make exactly the same progress in school, are remote indeed. School
children are, therefore, inevitably different.

V Age Distribution in One Grade

A very effective illustration of the differences in chronological age,
in school age, and in the rate of progress in school is furnished in the
1911 report of the superintendent of schools for Springfield, Mass.
There are in this report a series of figures dealing with the ages, and
time in school, of fifth-grade pupils in Springfield. The first table
shows the number of years in school and the age of all the fifth-grade
pupils.

TABLE 1

_Age and Time in School, Fifth Grade, Springfield, December, 1911_

Years in Ages
School 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Total
-----------------------------+---+-----------------------------------
1 .. .. .. .. .. ..| 1| .. .. .. .. .. .. .. 1
2 .. .. .. 2 1 1| 1| 2 2 .. .. .. .. .. 9
3