Understanding the nature of brain development in adolescence helps explain why adolescents can vacillate so often between mature and immature behavior. Early and middle adolescence, in particular, are times of heightened vulnerability to risky and reckless behavior because the brain's reward center is easily aroused, but the systems that control…

Summarizes school readiness and retention research issues, including youngest first graders' performance, entrance age policies, voluntary decisions to wait an extra year, assessment of children's readiness, and the negative effects of kindergarten and first-grade retention. Concludes that age disadvantages are seldom serious and usually disappear…