The average 13-year-old boy is 2.2 inches taller than the average 12-year-old--
63.1 inches or 5 feet 3. Boys are an average 3.2 inches taller as 14-year-olds and another 2.1 inches taller as 15-year-olds, when they are 5 feet 8 on average. At 19 years of age, they are almost 5 feet 10, the CDC reports.
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