Adolescents deserve the same chance as the adults so far as gigs go. A more important factor is whether or not they are good enough. Now I don't think they should receive any leniency just because they are kids. They should be judged equally with adult regarding talent and skills.
Everyone has their own time to shine, and "childhood" is an arbitrary period. No everyone is the same, and there is no such thing as growing up too fast or too slow, as long as it isn't forced. Adolescence is the best time to pursue any dream because at this time your abilities are usually highest. Vocal deteroiration can start as early as 25.