For a total of eight minutes and forty seconds In compared to other boys his age, a 12-year-old kid who can run a mile in eight minutes and 40 seconds is in the 50th percentile. Any time quicker than 8:40 is regarded a good time since it places the youngster in the top half of his age group. Anything over nine minutes is considered fast for a boy his age. A 12-year-old boy can walk or run one kilometer (0.6 miles) in less than eight minutes. He is performing at a moderate pace. The first two minutes of running are very important because that's when you reach your peak speed. After that, you start losing energy at a constant rate regardless of how much or how little you eat or drink. A young athlete can improve his time by working out more often or trying different activities. For example, if a child can walk for an hour without stopping, he could try walking faster for a while to see how far he can go before needing to rest. A 12-year-old boy can still grow taller and build muscle mass. He may be already at his maximum height, but he could have a longer leg span which is measured along with his height to determine what league he can play in. For example, a 13-year-old boy who is 1.80 meters (6 feet 0 inches) tall and who has a leg span of 2.20 meters (7 feet 4 inches) can play basketball.