In a school drill, a number of children are asked to stand in a circle. They are evenly spaced and the 6th child is diametrically opposite the 16th child. How many children are made to stand in the circle?

The 6th and the 16th child divide the circle into two halves as it is given that the 6th child is diametrically opposite the 16th child. 

When we consider one of the two halves, it will contain students numbered from 7 to 15, i.e a total of 9 children. 

Similarly, the other side must also have 9 children.

Now, including the two pairs of 9 children at each half along with child numbered 6 and 16, we have a total of 9+9+2= 20 children.