This study assessed the prevalence of weapon-related behaviors and experiences in secondary schools in California, their intercorrelations, and predictors at the individual and school levels. This study is based on a representative sample of 889,726 secondary school students in California based on the California Healthy Kids Survey. Prevalence ranged from 3.1% of students carrying gun to 17.9% who saw another student with a weapon. In 3.3% of schools, more than 15% of students carried a weapon and in 5.8% of schools, 15% or more were injured or threatened with weapons. The strongest predictors were the number of transgender students, gang members, and victimized students, particularly those victimized because of their disability. A public-health approach is advocated.