Mentoring is often misconstrued as perfect advice at the perfect time. Real life mentoring is a little slower, and in a lot of neighborhoods, it is often missing entirely. A national survey found that roughly one in three young people grew up without any mentor at all, about 16 million youth, including 9 million considered “at-risk.” The gap is widest where time, means of transportation, and adult bandwidth are thinnest. The case for starting a mentoring relationship young is simple: trust...