I would encourage teachers who teach mindfulness to students to make it a regular practice themselves first as it is less a technique than a way of being. The children will see right through you if you do it otherwise.
I was a school counselor for many years and in times of great student stress I would teach meditation as part of stress management. The students said, "This is the best thing we have ever done, why is it not taught more?" A parent complained and said it was of the devil. I never did understand as focus, peace and kindness are not the usual attributes of the devil. I used a mindfulness bell in classrooms where there were a number of students who were labeled attention deficit disordered. It helped all the children to regulate their nervous systems and the teacher bought her own bell as the ADD labeled kids had respite from the hyper activity and began to focus more.
It is interesting how this idea of teaching children mindfulness brings up defensiveness in some people who feel that it is religion. There is no dogma nor teachings in mindfulness other than focus, peace and kindness which is really the core of most religions until they are claimed by dogmatic zealots. It is true mindfulness is a guiding practice brought to the West by Buddhist teachers who have generously given permission for mindfulness to be used wherever it is useful. It is certainly not all that Buddhism teaches and one of the founding principles is that no-one should proselytize. Another is an instruction to any practitioner to use their own minds to decide what is right for them. If it works do it. The Science of Mind conferences bring scientists and others together to compare research that will be of benefit to all people regardless of religion. The Contemplative Christians are always part of this discussion.
Fear and separation lead to anxiety and sometimes depression and people are suffering. Mindfulness is a useful antidote to suffering and as the young woman on the recent CBC interview said, "You get out of it what you put into it."