Officials at Mira Costa High School in Manhattan Beach unveiled a commemorative wall dedicated to all four victims.
Adenhart, Courtney Stewart, and Henry Pearson were killed by a drunk driver in 2009, just hours after Adenhart won impressively at Angels Stadium.
Jon Wilhite, who survived the crash but was badly injured, was present at the ceremony. Wilhite and Pearson both attended Mira Costa.
Angels star pitcher Jered Weaver was also there. He said the tragedy serves as an important reminder.
"Obviously drinking and driving is not something that's fake, it's real, it's out there in the world," said Weaver. "And it not only affects people that are involved in accidents, but it involves families everywhere. So you know obviously we need to try to put a stop to drinking and driving as much as possible, and this is obviously a step in the right direction."
Andrew Gallo, the driver who triggered the crash, was convicted of three counts of second-degree murder and sentenced to 51 years to life in prison.