ses.[27]

[27] See Chapter VI for further discussion of the school progress
possible to children of various I Q's.

Special study of the I Q's between 70 and 79 revealed the fact that a
child of this grade of intelligence _never_ does satisfactory work in
the grade where he belongs by chronological age. By the time he has
attended school four or five years, such a child is usually found doing
"very inferior" to "average" work in a grade from two to four years
below his age.

On the other hand, the child with an I Q of 120 or above is almost never
found below the grade for his chronological age, and occasionally he is
one or two grades above. Wherever located, his work is always "superior"
or "very superior," and the evidence suggests strongly that it would
probably remain so even if extra promotions were granted.

CORRELATION BETWEEN I Q AND THE TEACHERS' ESTIMATES OF THE CHILDREN'S
INTELLIGENCE. By the Pearson formula the correlation found between the
I Q's and the teachers' rankings on a scale of five was .48. This is
about what others have found, and is both high enough and low enough to
be significant. That it is moderately high in so far corroborates the
tests. That it is not higher means that either the teachers or the tests
have made a good many mistakes.

When the data were searched for evidence on this point, it was found, as
we have shown in Chapter II, that the fault was plainly on the part of
the teachers. The serious mistakes were nearly all made with children
who were either over age or under age for their grade, mostly the
former. In estimating children's intelligence, just as in grading their
school success, the teachers often failed to take account of the age
factor. For example, the child whose mental age was, say, two years
below normal, and who was enrolled in a class with children about two
years younger than himself, was often graded "average" in intelligence.

The tendency of teachers is to estimate a child's intelligence according
to the quality of his school work _in the grade where he happens to be
located_. This results in overestimating the intelligence of older,
retarded children, and underestimating the intelligence of the younger,
advanced children. The disagreements between the tests and the teachers'
estimates are thus found, when analyzed, to confirm the validity of the
test method rather than to bring it under suspicion.

THE VALIDITY OF THE INDIVIDUAL TESTS. The validity of eac