yeah, dont do it.

[SpringHill Riderz]

My son tried to jump the lawnmower when he was about 6 years old.
He had a old one with no blades on it, rode it alot around the yard
while I was mowing. I thought it was cool. He's 14 now, and rides
he's atvs around the yard while I mow.

I'm curious why he's riding the atv around rather than helping you mow the lawn.

He knows how to get around the "system" 

In my house he'd be learning how to get around on his own 2 legs and feet.

The grass grows on the outside