The equation \( f(x) = 1600(1.025)^x \) models the population of the school, where \( x \) represents the number of years since 2015.
To find the population of the school in the year 2015, we need to set \( x = 0 \) (since 2015 is the base year).
Substituting \( x = 0 \) into the equation:
\[ f(0) = 1600(1.025)^0 \]
Since any number raised to the power of 0 is 1:
\[ f(0) = 1600 \cdot 1 = 1600 \]
Therefore, the population of the school in the year 2015 was 1600.