Bynum attended St. Joseph High School, in Metuchen, New Jersey during his junior and senior year. For most of his freshman year, he attended West Windsor Plainsboro High School North located in Plainsboro, New Jersey. For the remainder of his freshman year and his sophomore year he attended Solebury School in Solebury, PA. He played in the 2005 McDonald's All-American game where he tallied 9 points and 5 rebounds. In his junior year of high school Bynum averaged 16. 0 points, 13. 0 rebounds, and 6. 0 blocks. As a senior, he averaged 22. 4 points, 16. 8 rebounds and 5. 3 blocks per game. During his junior and senior year at St. Joseph High School, Bynum finished his high school career averaging 19. 2 points, 14. 9 rebounds, and 5. 6 blocks in 32 appearances. He originally planned to attend the University of Connecticut on a basketball scholarship; however, the 17-year-old made the decision to go directly into the NBA and made himself eligible for the 2005 NBA draft, where he was selected by the Los Angeles Lakers.