We have a joke in my house that whenever the boys are out of sorts, we attribute it to puberty. It turns out, this might not be so funny. New research shows that boys, like girls, are reaching puberty earlier—as young as 9 in some cases.

A study released this month by the American Academy of Pediatrics found that boys are starting puberty nearly two years earlier than boys did a generation ago. The study analyzed reports from more than 200 doctors in 41 states who examined more than 4,000 boys during wellness checkups. Half the boys were white, one-quarter were African-American, and one-quarter were Hispanic. The average age of puberty for white and Hispanic boys was 10. The average age for African-American boys was 9.

The researchers don’t know why this is happening. They speculated it could be obesity, less physical activity, or chemicals in the food we eat. And the long-term health implications are also unknown.

This raises all sorts of issues. In many state schools, health classes don’t discuss sexual issues until the kids are in the fifth grade. But by then, many of these boys and girls have already reached puberty. And if kids are reaching sexual maturity earlier, how do we keep them from acting on their impulses before they are emotionally ready to handle an intimate relationship?

Raging hormones are no laughing matter.