Meditation, my teacher used to say, is a vacation that you can give to yourself every time you tune in. For me, it’s a relief from stress and worry, a chance to hear the whispers of my own intuition, and space for my feelings that have not yet formed into words. More and more people are using contemplative practices, including educators who want to prepare their students with “21stcentury skills.” But a review in the June issue of the prestigious journal Child Development Perspectives warns that we should wait before adopting contemplative practices in schools: there just isn’t enough evidence on the benefits of contemplative practices for children to justify its widespread adoption.

There are many forms of contemplative or mindfulness practices—like meditation, yoga, Tai Chi, and the newer Mindfulness Based Stress Reduction—and they vary widely, but all have in common an important way of concentrating attention. Practitioners are guided to focus on the emotions, thoughts or feelings that flow through their awareness, without judging or getting caught up in them. For adults, these practices have been shown to reduce stress and anxiety, alleviate pain and illness, and change areas of the brain that are related to regulating emotions, attention and mental flexibility. Meditation practice is even associated with the lengthening of the DNA telomeres, suggesting that it may slow aging at the cellular level.

The research on contemplative practices with schoolchildren, however, is a different story. According to Penn State researchers Mark Greenburg and Alexis Harris, there hasn’t been enough research on the subject, and what studies have been done lack scientific rigor. The majority of studies suffer from design flaws: small numbers of children, a wide range of practices, different kinds of control groups, and varying periods of practice, which makes it difficult or impossible to compare or draw conclusions. Many measures rely on self-report—where the children themselves describe the effects they experience—which yields questionable data since children often want to please adult questioners. Sometimes reports come from teachers or parents who, themselves, know about—or even participate in—the programs, another potentially biased source of feedback. And no studies look at the long-term effects of mindfulness practice in kids.

This is not to say there isn’t reason to hope that contemplative practices can benefit children.