Anecdotally, yes it does improve attention in class. I have friends who are teachers here in Australia and they are all massively in favour of the bans after a year of them being in place. The problem with the scoping review quoted in the article is that it conflates several different issues and suggests phone bans in schools are supposed to be a silver bullet for all of them. You are never going to solve the mental health and bullying problems with a phone ban that only lasts half of the day, five days a week. Those problems require much broader policy and greater responsibility from parents. Another problem is that research into the effect of smartphones on schooling (which does actually suggest improvements) generally focuses on test or exam results, which are not a reliable indicator of whether students are actually learning or gaining anything from the experience of school.