AS someone who was a teacher at A-level (age 16-18) in the UK for 17 years until last year.... I think you may be right in the best case scenario, but my experience is that the number of pupils who use smartphones (or the wider internet) as such is vanishingly small. Most people don't have the mental discipline to use it for the amazing academic tool it could be, and the bright, shiny things of social media etc fritter away their attention. I don't think the last argument ('they'll talk anyway') holds much water - it's possible for pupils to look as if they are working but are actually on a phone; other forms of interaction are much more easily detected (two or more kids talking, etc).

I was made redundant from both my (part time) teaching jobs around this time last year (through no fault of my own or performance, I hasten to add!) and I have ZERO intention of ever going back - my (anecdotal, of course) experience of the education landcape and students' interest and behaviour (which I feel is significantly due to the attention-leeching effects of their constant exposure to smartphones) led the last 3/4 years to be a horrible experience that I wouldn't repeat if they paid me double what I was previously earning. I sincerely hope I'm wrong, but I am greatly concerned about the effect that such technology (and unmonitored use most of the time) is going to have on those who have been exposed to it since a very early age (who will be coming through the education system in the next 10 years or so).