These abbreviations are used:

–  E1G(t) – enrolled children in the first grade in a given year;

– C9G(t) – received a certificate of basic general secondary education (completed 9 classes);

– C11G(t) – received a certificate of completion of general secondary education (completed 11 classes);

– CE10(t) – continued education in 10^th grade;

– CBC is a constant that characterizes the number of learners who for various reasons dropped out of any class of secondary school during the year. Its size is calculated according to column 8, Table 1.7.

Thus, the contingent of learners of secondary school increases by the number of children enrolled in the first grade, the number of children who continued their education in the 10^th grade after receiving a certificate of basic general secondary education annually. The decrease in the contingent is due to the number of children who received a certificate of basic general secondary education (graduated from 9^th grade), children who received a certificate of complete general secondary education (graduated from 11^th grade) and students who dropped out of school any grades of secondary school during the year for various reasons.

To predict the contingent of secondary school learners, the actual and forecast data are summarized in Table 1.7.