The goal of this clinical trial is to evaluate whether the optimization of daily exposure to light in primary school children can lead to better myopia prevention and control. The trial also aims to better understand the impact of light exposure on sleep and cognitive performance in children. This trial has 3 arms namely, (1) a technical intervention arm, (2) a digital intervention arm, and (3) a control arm. 1. technical intervention - which involves changing of classroom lighting in primary schools to ceiling lights that mimic the spectral composition of sunlight and fluctuates in intensity. Parents of children within that arm will have a sham smart-phone application (s-LightUP) 2. digital intervention - which involves standard classroom lighting and giving parents an interventional smart-phone application (i-LightUP) that will be coupled with their child's light and activity sensor (wrist worn device ). The interventional app will provide individually tailored recommendation based on their children's behaviour (data feedback that is collected from the light and activity monitoring watch). The interventional app would then send reminder prompts/notifications to encourage parents help their children achieve required amounts of myopia-preventive light quantum target set per day. 3. Standard care or control group which involves standard classroom lighting and parents having a sham smart-phone application (s-LightUP) Participants will: * be randomised to receive either no intervention (control group), technical intervention (light intervention that mimics sunlight) or digital intervention (parents having an app that syncs with child's light and activity sensor which will provide feedback to parents to encourage and recommends increment of outdoor activities and hours). * have their myopia progression monitored every 6 monthly and cognitive assessment done once every 3 months over a year. * wear the light and activity sensor watches throughout the 1-year study period as much as possible (minimum 1 week per month) except for wet water activities such as swimming, diving and showering for research data collection purpose.