It was my third or fourth game, under 13s, now over a year ago, and it was 3-3 in the last minute, yellow v purple as yellow's striker charges into the box and his chopped by purple's defender. I point to the spot and there are no complaints, just slight annoyance that a point may be lost. I tell the goalkeeper to stay on his line, make sure I and he know the identity of the penalty taker and turn away, like a novice forgetting to tell him to wait for the whistle. At this point I assumed a 13 year old who was interested in football would know to wait for the whistle but he didn't. As I'm turning around I see his foot strike the ball. Now I'm praying it goes in so he can retake. It doesn't. The penalty is poor and the keeper holds it and boots it high and far. I decide that as it was a foul penalty I would play advantage. Anyway, it's too late now as purple's striker is through on goal. Fortunately it is saved and out for a corner which yellow clear and I end it there, to see the penalty taker in tears on the spot, 13 year olds and their parents surrounding me demanding an explanation and a long way back to the car. Was I right to play advantage or should he have retaken it? Either way, since then every penalty taker has been greeted by me saying very loudly "Wait. For. My. Whistle".