My son is doing this non-stop: water bottle flipping! The way it works is you take a water bottle that's about 1/3 full and try to flip it in the air and have it land on its base. I know...dumb!

But, he and his friends do it constantly. I kept hearing it while he was in his bedroom and couldn't figure out what the repeated "thud" sound was. My wife mentioned this on Facebook and other parents noticed their kids doing it too--but didn't know why.

A schoolteacher she's friends with said her students are always getting into trouble for flipping water bottles in class and at the lunch tables, and now they're giving out detentions to deter kids from doing it.