The scheme was laid.
They lit the rocket and skittered back from the wheel of sparks they expected. But their expectations were dashed. Instead of watching the rocket spin around its tether, a different experience was in store for them. The flame of the rocket propulsion quickly burnt through the yarn, and the rocket found a new trajectory straight into a vulnerable stomach.
The boy was alternately clutching his gut in pain, and smacking it to remove the rocket and extinguish the flames. He came away from the experience with a large bruise and a ruined, and hastily hidden, shirt. The boys never told their parents what they did.
Here's the kicker: They had graduated from high school the day before!
Reader comment: "The protagonist is my ex-boyfriend. You can see why I'm glad I am no longer in line to assist in propagating his genes!"