Scout tells Jem that Walter Cunningham jr. Made scout start off on the wrong what?

Scout says that Walter Cunningham made her start of on the wrong foot.

Catching Walter Cunningham in the schoolyard gave me some pleasure, but when I was rubbing his nose in the dirt Jem came by and told me to stop. “You’re bigger’n he is,” he said.

“He’s as old as you, nearly,” I said. “He made me start off on the wrong foot.”