Step in while a child is only starting to wind up, and offer something calming rather than a correction. Slow breathing, counting, a soft toy, a quiet corner for a few minutes.

What the research says

A systematic review with meta-analysis and meta-regression of mindfulness based approaches in ADHD found promising effects beyond the core symptoms, including on associated difficulties and on functioning. That gives some support to breathing and attention practices being worth teaching in a group where they are often written off as unrealistic. Most of that work is with older participants, and promising is the accurate word, so keep expectations sensible.

Strength of evidence: one line of research. A single study, or a theoretical account.