Prior to Stanford
- A 2023 graduate of Brentwood High School in Los Angeles
- Captained his team as a senior
- Three-time First Team All-League (2021, 2022, 2023)
- Second Team All-League (2020)
- Played for Rockstar Volleyball Club
- Placed third at AAU Nationals (2022)
- Runner-up finish in Milwaukee National Tournament (2022)
- Took third in 2022 SoCal Cup
Personal
- Parents are Michael Mandelbaum and Carlyn Henry
- Has a younger brother, Teddy
- Full name is Gray Michael Mandelbaum