A survey by nonprofit organization Common Sense Media shows 42% of children in the U.S. have a phone by the age of 10. And numbers like this are causing concern for educators, including a group of headteachers in Greystones, a town in Ireland. That group was so worried by the increased levels of anxiety among children using smartphones and social media that last year they asked parents to sign a voluntary pledge to delay buying cellphones for their children until at least the age of 11. The BBC’s Leanna Byrne checks in to see what effect it had.