Woodward — Public Schools: WitJidraival Age of Pupils. 187 



St. Louis that 52 per cent of those who were reported to me as 

 " 1(5 years old and over " were 16 years old; 30 per cent were 

 17 years old ; 13 per cent were 18 years old ; 5 per cent were 

 *' 19 years old and over." This distribution is made for each 

 of the numbers at the bottoms of several columns in Table I. 



In the case of the Chicago schools I assumed that 63 per 

 cent of those who were enrolled as <' 17 years old and over" 

 were 17 years old : 27 per cent were 18 years old ; 10 per cent 

 were "19 years old and over." This, I may say in paren- 

 thesis, corresponds to the distribution in the St. Louis 

 schools for those three years. This method of distribution 

 is applied to the last numbers in several columns in Table II. 

 The fact that nearly all of these tables show the withdrawal 

 of the 20-year-old pupils in the years 1895-6, and even later, 

 was an inevitable consequence, but the results are not on that 

 account to be called in question. All my results are based 

 upon averages, and are the consequence of laws which vary 

 very slightly from year to year in any given city. 



6. Other data essential to my calculation are: First, the 

 rate at which the population is increasing on account of the 

 excess of the number of births over the number of deaths. 

 Secondly, the rate at which the population is increasing, or 

 diminishing, from all causes, whether by accession of new ter- 

 ritory, the moving in or the moving out of children, or from 

 births or deaths. The internal growth (by which I mean 

 that arising from the excess of births over deaths) I calcu- 

 late from data furnished by the city officials. The growth 

 from excess of immigration over emigration and death, added 

 to the growth from the accession of new territory (as in the 

 case of Chicago in the year 1889) I call the " external 

 growth." The total growth is, of course, the sura of the 

 "internal" and "external" growths. I may here remark 

 that the growth in school population shown by the enrollment 

 in the public schools may differ from that shown by a general 

 census. There may be a general movement towards private 

 schools, or from private schools. When a pupil leaves a pub- 

 lic school and enters a private one, he practically "emigrates ;" 

 when he enters the public schools in one of the higher grades, 

 he practically "immigrates." 



