The Equation of the line turns out to be

And the x-intercept is the point (x, 0) and it is given by

which gives

Hence, the x-intercept is (-27,0)
This means 27 seconds before departure the distance from the school is 0.
Putting this in another way, we can also say that 27 is the time it takes to reach the school; Hence, the correct option is the second one.