The figures in the column at the right of the table represent the number of native born men between the ages of 21 and 45 among each hundred native born male inhabitants engaged in the occupations comprehended in the various groups.  In the case of the industrial group the figure is too high, as the census data relative to the distribution of foreign and native born include all ages, and there is a smaller proportion of American born adult men employed in industry than is found in the lower age groups.  Extensive computations have shown, however, that the inaccuracies due to this cause are not serious enough to affect the use of the figures for our purpose.

Let us now consider what these proportions mean in establishing vocational courses to prepare boys for wage-earning pursuits.  The future expectations of the boys in a large elementary school enrolling say 1,000 pupils of both sexes would be about as follows: 

Number of boys who will enter
    Manufacturing and mechanical occupations 220
    Commercial occupations 100
    Clerical occupations 80
    Transportation occupations 55
    Domestic and personal service occupations 25
    Professional occupations 15
    Public service occupations 5
          
                                              ——­
        Total 500

This distribution includes all pupils, from the beginners in the first grade to the older boys in the seventh and eighth grades.  It is certain, however, that differentiated instruction for vocational purposes is not possible or advisable for the younger children.  According to the commonly accepted view among educators, vocational training should not be undertaken before the age of 12 years, and many believe that this is too early.  In an elementary school of 1,000 pupils there would be about 80 boys 12 years old and over.  Applying to this number the ratios given in the previous table we obtain the following: 

Number of boys who will enter
    Manufacturing and mechanical occupations 35
    Commercial occupations 16
    Clerical occupations 13
    Transportation occupations 9
    Domestic and personal service occupations 4
    Professional occupations 2
    Public service occupations 1
          
                                               —–­
        Total 80

The industrial group includes all of the skilled trades and most of the semi-skilled and unskilled manual occupations.  The skilled trades are usually grouped in four main classifications:  metal trades, building trades, printing trades, and “other” trades, these last comprising a number of small trades in each of which relatively few men are employed.  With respect to their future occupations the 35 boys in the industrial group are likely to be distributed about as follows: