I played coed indoor soccer at one point in my pre-mother life and was hastily made keeper so that we could have a (faster, more skilled) guy on the field.
I had to learn to tend goal quickly. The most important thing, I realized, was to keep my eyes on the ball, not the game. It's more interesting to watch the game, more terrifying (or reassuring) to watch the clock, and hopeful to watch the score, but the important thing is to know where the ball is. It doesn't matter where the ball used to be. What matters is where it is now, and where it's going. Grading schools is like watching anything but the ball while tending goal.