Richard Lane, head of Manor Primary School in Drayton Bassett, Tamworth, arranged for his pupils to take some time out to learn about kite flying from an expert.
But one of the kites' strings broke, causing it to fly into a nearby power line and spark an electricity blackout.
"It was behind the tree and when he tugged the string it flew off into the power line," the head said. "I heard a bang - I'm sure it was the kite. I couldn't find it afterwards.
"All the alarms went off in the village. I can only apologise if it caused any inconvenience but I'm sure it was just a few seconds."
Mr Lane added that he hoped the experience had taught his pupils a valuable lesson in safety.
"It is important they don't play near to power lines," he said.