Schools now routinely use apps and technology to upload/download homework, notes etc (secondary school that is). I’d imagine that in a world where mobile technology is being used to enhance learning, then the children being able to access said technology when appropriate would be logical?
So my DD in her later stages of education would check and uploads etc at the end of a lesson, and as other have said take a picture of the whiteboard for notes etc.
Many of her peers actually put study notes (stuff I’d have had on flash cards for revision) on their phone and will study en route to school - they regularly test one another, more so at exam time.
Additionally some children were allowed to audio record lessons where given permission to enhance learning.
Obviously chatting and social media is a distraction, but instead of trying to ban phones, maybe embracing the advances in technology as some schools have done would help with engagement in the curriculum.