Forecasting of the indicator «Received a certificate of complete general secondary education» (completed eleven grades) will be carried out according to three algorithms with the basic indicator «Children enrolled in the first grade». First, it is necessary to calculate the average deviation of the indicator projected from the baseline (ADBL). We take the value of the indicator «Children enrolled in the first grade» from 2003 to 2008, which corresponds to 2014–2019 according to the projected indicator. In **Table 1.4**, columns 4 and 9, respectively. The average deviation of ADBL is 188.8 thousand people. Predicted values are given by the first algorithm of «mean deviations» in **Table 1.6**, column 4.

According to the second algorithm, the forecast data of the indicator «Received a certificate of complete secondary education» (graduated from 11 classes) in the interval 2020–2024 are calculated using polynomial (1.1): in which the free member is reduced by 188.8 thousand people:

*t* takes the value 7–11, which corresponds to 2020–2024.

In the interval 2025–2031, the forecast data of the indicator «Received a certificate of complete secondary education» (graduated from 11 classes) are calculated using polynomial (1.2), but the free member of this polynomial is reduced by 188.8 thousand people:

where *t* takes the value 1–7, which corresponds to 2025–2031 years.

The results of calculations according to the second algorithm are presented in column 5 of **Table 1.6**.

The third algorithm for predicting the indicator «Received a certificate of complete secondary education» (graduated from 11 classes) is not tied to the indicator «Children enrolled in the first grade», but is based on the model obtained by approximating the actual data for 2014–2019. Using the above package, synthesized polynomial:

where Z11 – «Received a certificate of complete secondary education» (graduated from 11 grades); *t* varies from 1 to 6, which corresponds to the interval 2014–2019, where the approximation process is implemented, and from the values of *t* from 7 to 11, which corresponds to the time interval from 2020 to 2024, the extrapolation process is implemented.

The model is statistically qualitative according to Fisher’s criterion and coefficient of determination.

Forecast data are presented in column 6, **Table 1.6**.