Nancy Carlson 
Loudmouth George and the Big Race, 2nd Edition [PDF ebook] 

Ready. Set. GO! Loudmouth George has told everyone he’s going to win the big race. He’s so confident that he doesn’t even bother to train. And on the day of the race, George ends up being the big loser. He’s put his foot in his mouth once again! George never seems to learn his lesson, but readers will get the point that a little effort-and modesty-can go a long way.