Deerfield has freshman place their phones in a basket during study hall. Lights out is at 10:30 for Freshman. During Sophomore year, the phones are supposed to be in the hallway outside your door. I believe WiFi turns off at 11:30 or midnight. No phones allowed during sit down meals.
To the OP - if your student is too dependent on technology & games, this will be an issue at boarding schools if he doesn’t know how to manage time effectively.