"In the HLM (Hierarchical Linear Modeling) analyses for students in grades eight, 10, and 12, drug testing (of any kind) was not a significant predictor of student marijuana use in the past 12 months. Neither was drug testing for cause or suspicion."
Source
Yamaguchi R, Johnston LD, O'Malley PM. Relationship between student illicit drug use and school drug-testing policies. J Sch Health. 2003;73(4):159-164. doi:10.1111/j.1746-1561.2003.tb03596.x
