An expert on the teenage brain says adolescents know drinking, sex and drugs are dangerous, but are wired to take risks. I talk to the researcher about how the key to keeping adolescents safe may not be more education about risky behaviors but fewer opportunities for such behaviors. A guest columnist says American students have to develop a global outlook to succeed in today’s economy. And readers sound off on whether teachers ought to supply forgetful students with pencils, pens and calculators in class.