All road events that juniors (ages 10-18) enter will have a rollout test of the riders gearing, and it is 26 feet, 0 inches. The chainring/cog combinations that typically work are 45/12, 48/13, and 52/14, provided you use a standard 23mm tire. THE REAL DISTANCE OF YOUR GEARING IS THE ROLLOUT TEST. . . how far the bike travels with one complete pedal revolution.
Many stock bikes come with a 53 chainring, which will most probably NOT pass the rollout test. Save time at the start line this year by checking rollout at home and adjusting your gearing before the race.