Lull grew up in Manhattan Beach, California and focused on surfing before turning his attention to basketball.[1] He attended Rolling Hills Preparatory School in San Pedro, California for three years. As a sophomore, Lull averaged 18.8 points and 12.8 rebounds per game, helping the Huskies reach the Southern Section 5A championship game. He averaged 15.4 points, 12.3 rebounds and 3.0 blocks per game as a junior. Lull transferred to New Hampton School for his senior year and also a postgraduate year. He committed to San Francisco in November 2015.[2]
College career
Lull came off the bench for his first two seasons at San Francisco. Following his sophomore season, he improved his conditioning by running up mountains in New Hampshire.[3] As a junior, Lull averaged 8.5 points and 5.3 rebounds per game.[4] On November 30, 2019, Lull scored a career-high 24 points and grabbed 10 rebounds in an 85–75 loss to Hawaii.[1] He averaged 11.9 points and 7.6 rebounds per game as a senior.[5] Lull was named Honorable Mention All-West Coast Conference.[6]