Homework is high-tech, with caveats

Drawbacks include worries about phone addiction, children's eyesight

On a recent Thursday evening, Zhang Yu, a fifth-grade student in Tianjin, braced himself for math assignments.

He had to use his mother's cell phone to do the assignment, because the three geometry problems concerning parallel lines were handwritten by his teacher on a piece of paper, then photographed and posted to a parent-teacher group on WeChat.