Students at a Portland high school are enrolled in a for-credit, year-long mindfulness class meant to ease youth anxiety and depression and to prevent violence.

The idea behind mindfulness is that focusing on the helps a person deal better with stress, difficult emotions and .

Mindfulness, yoga and meditation have become hugely popular in recent decades, buoyed by studies showing their benefits to emotional, mental and . It's practiced by corporate managers, prison inmates, hospital patients and the U.S. Marines.

Now many schools around the country are introducing them.

Some critics have complained the practices are too closely linked to Eastern religion, and at least one school has pulled them. But school districts report success, crediting mindfulness with curbing detentions and boosting attendance and academic achievement.